Viruses and the Macintosh

by David Harley

Version 1.6: 12 September 1999

Significant changes from the previous version are flagged with + symbols in the first two columns at the start of the relevant line or section. Amendments of minor grammatical or syntactical errors are not flagged unless they affect factual accuracy or clarity.

++ Sections tagged with [DH] or [SL] usually denote personal opinions or other data which the originator didn't feel the other maintainer should be held responsible for. Untagged sections using the first person are usually hangovers from when DH was sole maintainer of the FAQ.

++ Sadly for the rest of us, Susan Lesch has decided to take a break from co-maintaining this FAQ and from maintaining her "Mac Virus" website, and this version of the FAQ is mainly intended to reflect those changes. Susan has done the lion's share of the maintenance of this document for the last couple of years, and done a fantastic job. I shall miss her input, and the Mac community will be the poorer for the absence of her website. Thank you, from all of us.

++ I can't promise to give the FAQ the time I'd need to keep it as topical as it has been, so the next revision will be focused on updating core material and checking URLs rather than news. What happens after that depends on a number of plans that are still taking shape.

David Harley

Table of Contents

1.0 Copyright Notice

Copyright on this document remains with the author(s), and all rights are reserved. However, it may be freely distributed and quoted - accurately, and with due credit.

It may not be reproduced for profit or distributed in part or as a whole with any product for which a charge is made, except with the prior permission of the copyright holder(s). To obtain such permission, please contact the maintainer of the FAQ.

Primary author and maintainer of this document is David Harley, Comments and additional material have been received with gratitude from Ronnie Sutherland, Henri Delger, Mike Groh and Eugene Spafford. Thanks to Bruce Burrell, Michael Wright, Peter Gersmann, David Miller, Ladd Van Tol, Eric Hildum, Jeremy Goldman, Kevin White, Bill Jackson, Robert Slade, Robin Dover, and John Norstad for their comments and suggestions. Special thanks to Susan Lesch for her contributions, editing, and maintenance chores as co-maintainer.

2.0 Preface

This document is intended to help individuals with computer virus-related problems and queries, and clarify the issue of computer viruses on Macintosh platforms. It should not be regarded as being in any sense authoritative, and has no legal standing. The authors accept no responsibility for errors or omissions, or for any ill effects resulting from the use of any information contained in this document.

Corrections and additional material are welcome, especially if kept polite.... Contributions will, if incorporated, remain the copyright of the contributor, and credited accordingly within the FAQ.

David Harley <D.Harley@icrf.icnet.uk>

3.0 Availability of this FAQ

++ The latest version of this document is currently still available from However, the primary source is now It's also available from Henri Delger's Prodigy Anti-Virus Center file library, as is the alt.comp.virus FAQ.

++ There are HTML versions at:

++ I have no control over the content of these sites, and can't guarantee that they're up-to-date.

4.0 Mission Statement

This document is a little different to the alt.comp.virus FAQ, which David Harley also co-maintains (at time of writing). It is concerned with one platform only, and though it deals with the Macintosh platform at more length than the alt.comp.virus FAQ can be expected to, it is a great deal shorter. Nor is there the same degree of urgency about the Mac virus field, though the risk element may be somewhat underestimated in general, at present. This FAQ originated from a concern over the spread of macro viruses, a theme that is taken up below. Since questions about Macs and viruses tend to appear more often in the Mac groups than alt.comp.virus or Virus-L, distribution of this FAQ is wider.

5.0 Where to get further information


5.1 Computer Virus FAQs

Computer Virus FAQ for New Users
A mainly non-Mac virus FAQ posted to news.newusers.questions, alt.newbie, alt.newbies, alt.answers, and news.answers. alt.comp.virus FAQ
This is posted to alt.comp.virus approximately fortnightly. It includes a document that summarizes and gives contact information for a number of other virus-related FAQs; (not much Mac-specific material). The latest version is available from: VIRUS-L/comp.virus FAQ
The Virus-L/comp.virus FAQ (also fairly low on Mac-specific information) is regularly posted to the comp.virus newsgroup (version 2.0 at time of writing). This FAQ is very long and very thorough. The document is subject to revision, so the file name may change. The latest version may be found at:

5.2 EICAR

++ Dr Solomon's Anti-Virus Toolkit, Virex, and NAV (Norton AntiVirus for Macintosh) now support the EICAR test. This article by Paul Ducklin of Sophos explains the EICAR test file:

5.3 "Robert Slade's Guide to Computer Viruses"

The disk included with the 2nd Edition of this excellent general resource includes most of the information available at the University of Hamburg (see 5.5). The book also contains a reasonable quantity of Mac-friendly information. The disk includes a copy of Disinfectant 3.6, which is now out-of-date -- 3.7.1 is the latest and final release. For more information about this book: ++ Very few books primarily about computer viruses deal at any length with Mac viruses (I can't think of one, at present). Some general books on the Mac touch on the subject, but none I can think of add anything useful. Some of the "Totally Witless User's Guide to......." books dealing with security in general include information on PC and Mac viruses. Unfortunately, the quality of virus-related information in such publications is generally low, and there are few or no books on computer viruses in general which are both recent and accurate.

5.4 Web sites

Many major vendors have a virus information database online on their Web sites. Symantec (www.symantec.com), Network Associates (www.nai.com), Sophos (www.sophos.com) and Dr. Solomon's (www.drsolomon.com) include Macintosh virus information.

Precise URLs tend to come and go, but you might like to try the following:

5.5 Virus Bulletin

The expensive (but, for the professional, essential) periodical Virus Bulletin includes Mac-specific information from time to time. However, if you have no interest in PC issues, you probably won't consider it worth the expense. The proceedings of the 1997 Virus Bulletin conference contained a paper by David Harley which significantly expands on many of the issues addressed in this FAQ. Contact Virus Bulletin for further information on the annual conference and on obtaining the proceedings. The paper can also be found (by permission of Virus Bulletin) at the author's website:

5.6 Macro virus information resources

University of Hamburg Virus Test Center Macro Virus List is the definitive listing. All known macro viruses, some only found in research labs, some in the wild. Doesn't include information on individual viruses apart from name and platform. Other Sources: [The following absolute URLs may change: such is the way of Web administrators..... If you get an error message, try the first part of the URL, e.g. <http://www.nai.com/> and drill down from there.] ++ Richard Martin put together an FAQ on the subject of Word viruses. It's well out-of-date, though, and was always inaccurate in some respects. ++ This URL may be out of date. There is a copy of what I believe to be the last released version at www.sherpasoft.com:

5.7 Other resources

There are excellent pages on HyperCard viruses at HyperActive Software. There is information on HyperCard infectors, a link to Bill Swagerty's free Vaccine utility for detecting and cleaning them, a note on false positives reported by commercial software, inoculation, and a free HyperCard virus detection service. The CIAC virus database includes entries for PC, Macintosh, and a number of other platforms. The Macintosh section also includes a number of joke programs and one or two apparent hoaxes. Virus Test Center, Hamburg: AntiVirus Catalog/CARObase early work These links may be out-of-date: if they don't work, try Last we checked [03-Sep-97], these sites probably need updating, though some older files do have historical value. Info-Mac mirrors have Macintosh information, but includes some outdated virus information and software at this writing; still, always worth a visit. Also of interest, again sometimes outdated: Kevin Harris's Virus Reference was last updated 31-Aug-95. This HyperCard stack requires HyperCard 2.1 or later.

6.0 How many viruses affect the Macintosh?

There are around 40 Mac-specific viruses and related threats.

Mac users with Word 6 or versions of Excel supporting Visual Basic for Applications, however, are vulnerable to infection by macro viruses which are specific to these applications. Indeed, these viruses can, potentially, infect other files on any hardware platform supporting these versions of these applications. I don't know of a macro virus with a Mac-specific payload that actually works at present, but such a payload is entirely possible.

++ Office 98 applications are in principle vulnerable to most of the threats to which Office 97 applications are vulnerable. I'll return to this subject when and if time allows. [DH]

Word Mac version 5.1 and below do not support WordBasic, and are not, therefore, vulnerable to direct infection. Not only do these versions not only understand embedded macros, but they can't read the Word 6 file format unaided. There is, however, at least one freeware utility which allows Word 5.x users to read Word 6 files. This will not support execution of Word 6 (or WinWord 2) macros in Word 5.x, so I would not expect either an infection routine or a payload routine to be able to execute within this application.

However, Word 5.x users may contribute indirectly to the spread of infected files across platforms and systems, since it is perfectly possible for a user whose own system is uninfectable to act as a conduit for the transmission of infected documents, whether or not s/he reads it personally.

Files infected with a PC-specific file virus (this excludes macro viruses) can only execute on a Macintosh running DOS or DOS/Windows emulation, if then. They can, of course, spread across platforms simply by copying infected files from one system to another.

DOS diskettes infected with a boot sector virus can be read on a Mac with Apple File Exchange, PC Exchange, DOS Mounter etc. without (normally) risk to the Mac. However, leaving such an infected disk in the drive while booting an emulator such as SoftPC can mean that the virus attempts to infect the logical PC drive with unpredictable results.

I am aware of at least one instance of a Mac diskette which, when read on a PC running a utility for reading Mac-formatted disks after being infected with a boot-sector infector, became unreadable as a consequence of the boot track infection.

Some Mac viruses may damage files on Sun systems running MAE or AUFS.

7.0 What viruses can affect Mac users?

Not all variants are listed here. It was originally intended to reference all the major variants at least by name eventually, but since the information is of academic interest at best to most users (and available elsewhere anyway), it's no longer considered a priority. The main problem affecting Mac users nowadays is the spread of macro viruses, and I can't possibly find time to catalogue them individually, so they are only considered generally. Native Mac viruses are rather rarely seen nowadays, and most people don't need to know about them in detail -- in fact, what they need most is to know that their favoured antivirus software will deal with them. Note that I'm not primarily in the business of hands-on virus analysis, and cannot accept responsibility for descriptive errors based on third-party information. [DH]

The following varieties are listed below:

7.1 Mac-specific system and file infectors

AIDS - infects application and system files. No intentional damage. (nVIR B strain)

Aladin - close relative of Frankie

Anti (Anti-A/Anti-Ange, Anti-B, Anti Variant) - can't spread under system 7.x, or System 6 under MultiFinder. Can damage applications so that they can't be 100% repaired.

CDEF - infects desktop files. No intentional damage, and doesn't spread under system 7.x.

CLAP: nVIR variant that spoofs Disinfectant to avoid detection (Disinfectant 3.6 recognizes it).

Code 1: file infector. Renames the hard drive to "Trent Saburo". Accidental system crashes possible.

Code 252: infects application and system files. Triggers when run between June 6th and December 31st. Runs a gotcha message ("You have a virus. Ha Ha Ha Ha Ha Ha Ha Now erasing all disks... [etc.]"), then self-deletes. Despite the message, no intentional damage is done, though shutting down the Mac instead of clicking to continue could cause damage. Can crash System 7 or damage files, but doesn't spread beyond the System file. Doesn't spread under System 6 with MultiFinder beyond System and MultiFinder. Can cause various forms of accidental damage.

Code 9811: hides applications, replacing them with garbage files named "something like 'FIDVCXWGJKJWLOI'." According to Ken Dunham who reported this virus in November, "The most obvious symptom of the virus is a desktop that looks like electronic worms and a message that reads 'You have been hacked by the Pretorians.'"

Code 32767: once a month tries to delete documents. This virus is not known to be in circulation.

Flag: unrelated to WDEF A and B, but was given the name WDEF-C in some anti-virus software. Not intentionally damaging but when spreading it overwrites any existing 'WDEF' resource of ID '0', an action which might damage some files. This virus is not known to be in circulation.

Frankie: only affects the Aladdin emulator on the Atari or Amiga. Doesn't infect or trigger on real Macs or the Spectre emulator. Infects application files and the Finder. Draws a bomb icon and displays 'Frankie says: No more piracy!"

Fuck: infects application and System files. No intentional damage. (nVIR B strain)

Init 17: infects System file and applications. Displays message "From the depths of Cyberspace" the first time it triggers. Accidental damage, especially on 68K machines.

Init 29 (Init 29 A, B): Spreads rapidly. Infects system files, applications, and document files (document files can't infect other files, though). May display a message if a locked floppy is accessed on an infected system 'The disk "xxxxx" needs minor repairs. Do you want to repair it?'. No intentional damage, but can cause several problems - Multiple infections, memory errors, system crashes, printing problems, MultiFinder problems, startup document incompatibilities.

Init 1984: Infects system extensions (INITs). Works under Systems 6 and 7. Triggers on Friday 13th. Damages files by renaming them, changing file TYPE and file CREATOR, creation and modification dates, and sometimes by deleting them.

Init-9403 (SysX): Infects applications and Finder under systems 6 and 7. Attempts to overwrite whole startup volume and disk information on all connected hard drives. Only found on Macs running the Italian version of MacOS.

Init-M: Replicates under System 7 only. Infects INITs and application files. Triggers on Friday 13th. Similar damage mechanisms to INIT-1984. May rename a file or folder to "Virus MindCrime". Rarely, may delete files.

MacMag (Aldus, Brandow, Drew, Peace): first distributed as a HyperCard stack Trojan, but only infected System files. Triggered (displayed a peace message and self-deleted on March 2nd 1988, so very rarely found.

MBDF (A,B): originated from the Tetracycle, Tetricycle or "tetris-rotating" Trojan. The A strain was also distributed in Obnoxious Tetris and Ten Tile Puzzle. Infect applications and system files including System and Finder. Can cause accidental damage to the System file and menu problems. A minor variant of MBDF B appeared in summer 1997: Disinfectant and Virex have been updated accordingly.

MDEF (MDEF A/Garfield, MDEF B/Top Cat, C, D): infect System file and application files (D doesn't infect System). No intentional damage, but can cause crashes and damaged files.

MDEF-E and MDEF-F: described as simple and benign. They infect applications and system files with an 'MDEF' resource ID '0', not otherwise causing file damage. These viruses are not known to be in circulation.

nCAM: nVIR variant

nVIR (nVIR A, B, C - AIDS, Fuck, Hpat, Jude, MEV#, nFlu): infect System and any opened applications. Extant versions don't cause intentional damage. Payload is either beeping or (nVIR A) saying "Don't panic" if MacInTalk is installed.

nVIR-f: nVIR variant.

prod: nVIR variant

Scores (Eric, Vult, NASA, San Jose Flu): aimed to attack two applications that were never generally released. Can cause accidental damage, though - system crashes, problems printing or with MacDraw and Excel. Infects applications, Finder, DA Handler.

SevenDust-A through G (MDEF 9806-A through D, also known as 666, E was at first called "Graphics Accelerator"): a family of five viruses which spread both through 'MDEF' resources and a System extension created by that resource. The first four variants are not known to be in circulation. Two of these viruses cause no other damage. On the sixth day of the month, MDEF 9806-B may erase all non-application files on the current volume. The SARC encyclopedia calls MDEF 9806-C, "polymorphic and encrypted, no payload," and MDEF 9806-D, "encrypting, polymorphic, symbiotic," and says the symbiotic part, "alters a 'WIND' resource from the host application." SevenDust E, not to be confused with the legitimate ATI driver "Graphics Accelerator", began as a trojan horse released to Info-Mac and deleted there on or about September 26, 1998. Takes two forms, 'INIT' resource ID '33' in an extension named "\001Graphics Accelerator" and an 'MDEF' resource ID '1' to '255'. Between 6:00 a.m. and 7:00 a.m. on the sixth and twelfth day of any month, the virus will try to delete all non-application files on the startup disk. John Dalgliesh describes "Graphics Accelerator" on his Web page for AntiGax, a free anti-SevenDust E utility; any errors here in translation are not his. SevenDust F uses a trojan "ExtensionConflict", common extensions names, and creator 'ACCE'.[SL]

T4 (A, B, C, D): infects applications, Finder, and tries to modify System so that startup code is altered. Under System 6 and 7.0, INITs and system extensions don't load. Under 7.0.1, the Mac may be unbootable. Damage to infected files and altered System is not repairable by Disinfectant. The virus masquerades as Disinfectant, so as to spoof behaviour blockers such as Gatekeeper. Originally included in versions 2.0/2.1 of the public domain game GoMoku.

T4-D spreads from application to application on launch by appending itself to the 'CODE' resource. Deletes files other than the System file from the System Folder, and documents, and is termed dangerous. The D strain is not known to be in circulation [SL].

WDEF (A,B): infects desktop file only. Doesn't spread under System 7. No intentional damage, but causes beeping, crashes, font corruption and other problems.

zero: nVIR variant.

Zuc (A, B, C): infects applications. The cursor moves diagonally and uncontrollably across the screen when the mouse button is held down when an infected application is run. No other intentional damage is done.

7.2 HyperCard infectors

These are a somewhat esoteric breed, but a couple have been seen since Disinfectant was last upgraded in 1995, and most of the commercial scanners detect them.

Dukakis - infects the Home stack, then other stacks used subsequently. Displays the message "Dukakis for President", then deletes itself, so not often seen.

HC 9507 - infects the Home stack, then other running stacks and randomly chosen stacks on the startup disk. On triggering, displays visual effects or hangs the system. Overwrites stack resources, so a repaired stack may not run properly.

HC 9603 - infects the Home stack, then other running stacks. No intended effects, but may damage the Home stack.

HC "Two Tunes" (referred to by some sources as "Three Tunes") - infects stack scripts. Visual/Audio effects: 'Hey, what are you doing?' message; plays the tune "Muss I denn"; plays the tune "Behind the Blue Mountains"; displays HyperCard toolbox and pattern menus; displays 'Don't panic!' fifteen minutes after activation. Even sources which describe this virus as "Three Tunes" seem to describe the symptoms consistently with the description here, but we will, for completeness, attempt to resolve any possible confusion when time allows. This virus has no known with the PC file infector sometimes known as Three Tunes.

MerryXmas - appends to stack script. On execution, attempts to infect the Home stack, which then infects other stacks on access. There are several strains, most of which cause system crashes and other anomalies. At least one strain replaces the Home stack script and deletes stacks run subsequently. Variants include Merry2Xmas, Lopez, and the rather destructive Crudshot. [Ken Dunham discovered the merryXmas virus. His program merryxmasWatcher 2.0 was very popular and still can eradicate the most common two strains, merryXmas and merry2Xmas. merryxmasWatcher 2.0 is outdated for the rest this family.]

Antibody is a recent virus-hunting virus which propagates between stacks checking for and removing MerryXmas, and inserting an inoculation script.

Independance (sic) Day - reported in July, 1997. It attempts to to be destructive, but fortunately is not well enough written to be more than a nuisance. More information at:

Blink - reported in August, 1998. Nondestructive but spreads; infected stacks blink once per second starting in January, 1999.

7.3 Mac Trojan Horses

These are often unsubtle and immediate in their effects: while these effects may be devastating, Trojans are usually very traceable to their point of entry. The few Mac-specific Trojans are rarely seen, but of course the commercial scanners generally detect them.

ChinaTalk - system extension - supposed to be sound driver, but actually deletes folders.

CPro - supposed to be an update to Compact Pro, but attempts to format currently mounted disks.

+ ExtensionConflict - supposed to identify Extensions conflicts, but installs one of the six SevenDust a.k.a. 666 viruses.

FontFinder - supposed to lists fonts used in a document, but actually deletes folders.

MacMag - HyperCard stack (New Apple Products) that was the origin of the MacMag virus. When run, infected the System file, which then infected System files on floppies. Set to trigger and self-destruct on March 2nd, 1988, so rarely found.

Mosaic - supposed to display graphics, but actually mangles directory structures.

NVP - modifies the System file so that no vowels can be typed. Originally found masquerading as 'New Look', which redesigns the display.

Steroid - Control Panel - claims to improve QuickDraw speed, but actually mangles the directory structure.

Tetracycle - implicated in the original spread of MBDF

Virus Info - purported to contain virus information but actually trashed disks. Not to be confused with Virus Reference.

Virus Reference 2.1.6 mentions an 'Unnamed PostScript hack' which disables PostScript printers and requires replacement of a chip on the printer logic board to repair. A Mac virus guru says:

"The PostScript 'Trojan' was basically a PostScript job that toggled the printer password to some random string a number of times. Some Apple laser printers have a firmware counter that allows the password to only be changed a set number of times (because of PRAM behavior or licensing -- I don't remember which), so eventually the password would get "stuck" at some random string that the user would not know. I have not heard any reports of anyone suffering from this in many years."

AppleScript Trojans - A demonstration destructive compiled AppleScript was posted to the newsgroups alt.comp.virus, comp.sys.mac.misc, comp.sys.mac.system, it.comp.macintosh, microsoft.public.word.mac, nl.comp.sys.mac, no.mac, and symantec.support.mac.sam.general on 16-Aug-97, apparently in response to a call for help originally posted to alt.comp.virus on 14-Aug-97 and followup on 15-Aug-97. On 03-Sep-97, MacInTouch published Xavier Bury's finding of a second AppleScript trojan horse, which, like the call for help followup, mentioned Hotline servers. It reportedly sends out private information while running in the background. A note to users from Hotline Communications CEO Adam Hinkley is posted at

AppleScripts should be downloaded only from known trusted sources. It is nigh impossible for an average person to know what any given compiled script will do.

7.4 Macro viruses, trojans, variants

At the time of the longstanding second-to-last upgrade of Disinfectant (version 3.6 in early 1995), there were no known macro viruses in the wild, apart from HyperCard infectors. In any case, Disinfectant was always intended to deal with system viruses, not trojans or macro/script viruses. However, many users are unaware of these distinctions and still assume that Disinfectant is a complete solution, even after its effective demise (in fact, there were people still relying on Gatekeeper long after its author disowned it....).

++ Unfortunately, the number of known macro viruses runs into several thousand, though the number in the wild is far fewer.

Most macro viruses (if they have a warhead at all) target Intel platforms and assume FAT-based directory structures, so they usually have no discernible effect on Macs when they trigger. Viruses that manipulate text strings within a document may work just as well on a Macintosh as on a PC.

In any case, the main costs of virus control are not recovery from virus payloads, but the costs of establishing detection and protection (or of not establishing them). The costs of not establishing these measures can be considerable, irrespective of damage caused on infected machines, especially in corporate environments. Secondary distribution of infected documents may result in:

Since Word 6.x for Macintosh supports WordBasic macros, it is as vulnerable as Word 6.x and 7.x on Intel platforms to being infected by macro viruses, and therefore to generating other infected documents (or, strictly speaking, templates). Working Excel viruses are now beginning to appear also, and any future Macintosh application that supports Visual Basic for Applications will also be vulnerable. Note also that the possibility of virus-infected files embedded as objects in files associated with other applications: this possibility exists on any platform that supports OLE.

++ Office 98 is in general vulnerable to infection by most viruses which affect corresponding applications in Office 97.

Macro viruses are therefore highly transmissible via Macintoshes, even if they don't have a destructive effect on Motorola platforms, if there is an equivalent application available on the Macintosh. For instance, although Word for Windows versions before vs. 6 support WordBasic, Word versions for the Mac up to and including version 5.1 do not. [Thus Word 5.1 users can not be directly infected, but may, like anyone, pass on infected documents to vulnerable systems.]

++ [reference to Green Stripe removed]

Network Associates, Symantec, and Intego all make known-virus scanners that detect a range of macro viruses. Microsoft make available a free 'protection tool' whose effectiveness is often overestimated. (See below.)

For further information on specific macro viruses, try one of the information resources given earlier.

7.5 Other Operating Systems, emulation on a Mac

Any Mac running any sort of DOS or Windows emulation such as Virtual PC, SoftPC, SoftWindows, RealPC, or a DOS compatibility card is a potential target for any PC virus, including Boot Sector Infectors/Multipartites; (effects will vary). It is highly recommended that anyone with such a system should run a reputable, up-to-date PC antivirus program under emulation, as well as a good Mac antivirus program. [Dr. Solomon's for the Mac detects PC boot sector infectors as well as Mac viruses, but doesn't detect PC file viruses (apart from macro viruses), and so is not sufficient protection for a Mac with DOS emulation.]

Recommendations for defending PC systems or PC emulation on Macs are slightly out-of-scope for this FAQ. In fact, I don't know of any formal testing for PC antivirus software in the context of PC emulation on Macs. I've done some informal testing (referred to in another paper), but am not prepared to make vendor-specific recommendations on the basis of such testing. F-Prot, AVP, and Dr Solomon's are particularly well-regarded PC antivirus packages, of which some components on some platforms are available as freeware or for evaluation, but their efficacy in the context of PC emulation is not well tested or documented.

To find a commercial or shareware package relevant to PCs, check through the independent comparative reviews sites:

7.6 AutoStart 9805 Worms

AutoStart 9805 is not a virus, but a worm: that is, it replicates by copying itself, but doesn't attach itself parasitically to a host program. The original took hold rapidly in Hong Kong and Taiwan in April 1998, and has been reported on at least four continents. In addition to the original worm, there are five variants. Virus Bulletin, July, 1998, includes a comprehensive analysis of AutoStart and some of its variants.

CIAC Bulletin I-067 is based on Eugene Spafford's information release on the original AutoStart worm. Unfortunately,this is now a little out-of-date, particularly as regards the update status of the antivirus software it mentions. Nor does it mention any of the subsequently discovered variants.

Symptoms: Perhaps the most noticeable symptom of the worms is that an infected system will lock up and churn with unexplained disk activity every 6, 10, or 30 minutes.[SL]

Affected platforms: any PowerMac. Macintoshes and clones driven by Motorola 680x0 series CPUs can't run the replicative code. It works under any version of Mac OS, if QuickTime 2.0 or later is installed and CD-ROM AutoPlay is enabled in the "QuickTime Settings" Control Panel.

Transmission media: HFS or HFS+ volumes (hard disks, diskettes, most types of removable media, even disk images). Audio CDs can't transmit the virus, and it isn't necessary to disable "Audio CD AutoPlay".

Transmission method: infected media contain an invisible application file named "DB" or "BD" or "DELDB" in the root directory (type APPL, creator ????). This is an AutoStart file: i.e. it will run automatically if CD-ROM autoplay is enabled. If the host Mac isn't already infected, it copies itself to the Extensions folder. The new copy is renamed "Desktop Print Spooler" or "Desktop Printr Spooler", or "DELDesktop Print Spooler" respectively (type appe, creator ????). Unlike the legitimate Desktop Printer Spooler extension, the worm file has the invisible attribute set, and isn't listed as a running process by the system software, though it can be seen with Process Watcher or Macsbug. After copying itself, it reboots the system and is now launched every time the system restarts. At approximately 6, 10, or 30 minute intervals, it examines mounted volumes to see if they're infected: if not, it writes itself to the root directory and sets up AutoStart (however, AutoStart won't work on a server volume).

Damage: files with names ending "data", "cod" or "csa" are targeted if the data fork is larger than 100 bytes. Files with names ending "dat" are targeted if the whole file is c. 2Mb or larger. Targeted files are attacked by overwriting the data fork (up to the 1st Mb) with garbage.

Besides the original, there are five variants: AutoStart 9805-B, which is less noticeable but can cause irreparable damage to files of type 'JPEG', 'TIFF', and 'EPSF'; AutoStart 9805-C and AutoStart 9805-D which do not intentionally damage data; AutoStart 9805-E which spreads like B and is most similar to the original; and AutoStart 9805-F which is most similar to A and E. Dr Solomon's, Sophos, and Symantec had descriptions on the Web:

++ Dead Mac Virus link cleaned.

Detection: updates to deal with the worms are available for Virex (http://www.drsolomon.com/products/virex/), for NAV and SAM (http://www.symantec.com/avcenter/download.html), and for Rival (http://www.intego.com/).

++ The last versions of VirusScan for Mac and Disinfectant did not detect AutoStart. [Reference to Dr Solomon's for Mac removed, as the product is no longer supported.]

Prevention: uninfected systems can be protected by disabling the AutoStart option in QuickTime settings (QuickTime 2.5 or later only - earlier versions don't have a disable option). This should also prevent infection by future malware exploiting the same loophole, but will fail if a setup is booted from a volume with an infected Extensions Folder [SL].

Removal: the easiest and safest method for most people will be to use the updated version of their favoured anti-virus software, as it becomes available.

The worms can be also be removed manually.

7.7 Esperanto.4733

++ This probably doesn't belong here. It's a PC file infector which works with a number of PC executable file formats. When it was first seen, it was reported to be a multiplatform virus capable of executing under some circumstances on Macintoshes. Subsequent reports indicate that this belief results from misinformation on the part of the author. However, at least two reputable PC anti-virus vendors still list it as capable of activating on a Macintosh. No Mac scanner is known to attempt to detect it.

8.0 What's the best antivirus package for the Macintosh?

As ever, we can't give a definitive answer to this. The best choice depends on subjective criteria and individal needs. Nonetheless, Here are some thoughts on the main contenders.

8.1 Microsoft's Protection Tools

Microsoft's Macro Virus Protection Tools originally detected Concept (Nuclear and DMV were also mentioned in the documentation, but were not identified specifically by the tools). Principally, they merely warned users that the document they are about to open contained macros and offered the choice of opening the file without macros, opening it with macros, or cancelling the File Open. Later implementations built into the application are better on identifying a few specific viruses and on integration into Word itself, but should not be relied on for 100% effective detection, blocking and disinfection of macro viruses. More information from Microsoft may be available at the addresses below. NB The Protection Tool traps some File Open operations, but not all. There are a number of ways of opening a document which bypass it, some of which are rather commonly used (e.g. double-clicking or using the Recent Documents list).

The Protection Tool can be used to scan for Concept-infected files, but there are a number of possible problems with it.

Windows 95 users should be aware that SCANPROT is not recommended for use with MS Word 7.0a for Windows with internal detection enabled, as these two tools will cancel each other out.

The Excel add-in for Macs removes only Laroux A and B.

Office 98 moves the goalposts again. This issue will probably be addressed again here in more depth. In brief, Office 98 does a better job of implementing a primarily generic approach [i.e. "If it contains macros, it's suspicious: sort it out yourself...."], but whether this is enough is a question demanding more space and time than I have to spare right now [DH].

Microsoft's home page has recommended using an ICSA-certified antivirus utility and sidesteps any hint of responsibility for any macro virus or SCANPROT related problems.
(1) not everyone is happy with the current implementation of ICSA (NCSA) certification
(2) ICSA certification is not at present Mac-aware.

8.2 Disinfectant

[On May 6th 1998, John Norstad, author of this widely-used freeware package announced that it was to be retired. 3.7.1 is the latest and last version, and it won't be updated to detect AutoStart 9805 or any subsequent Macintosh malware. The main reason for this is that he doesn't have the resources to extend its capabilities to detect macro viruses, which have become by far the most significant virus problem for most Macintosh users.

This is probably a wise decision, given the number of people who still overestimate the effectiveness of the package in the face of the macro virus threat. However, the entire Macintosh community owes John Norstad a debt of gratitude for making it freely available for so long, an act of altruism which has probably contributed very significantly to the comparative rarity of native Macintosh viruses.]

Disinfectant was an excellent anti-virus package with exemplary documentation, and didn't cost a penny: however, it didn't detect all the forms of malware that a commercial package usually does, including HyperCard infectors, most Trojans, jokes or macro viruses. Unlike some commercial packages, it didn't scan compressed files, either: compressed files had to be expanded before scanning. Self-extracting archives were probably best scanned before unpacking, then again when unpacked.

Disinfectant has been available up to now from the following sources, but this may not continue to be the case.:

The Disinfectant README was updated to README-IMPORTANT on 6 May 1998, with the message, "because of the widespread and dangerous Microsoft macro virus problem," "...All Disinfectant users should switch..." to another program. README-IMPORTANT was updated again on 11 October 1998, adding, "In addition to the Autostart worm and the Microsoft macro viruses, several other new Mac viruses have appeared since Disinfectant's retirement in May. This makes it even more important that Disinfectant users switch..." to one of the commercial products. There is a copy of the retirement announcement on the Web:

8.3 Demo Software

Symantec has a 30-day fully-functioning trialware NAV (Norton AntiVirus for Macintosh). Update it with current definitions. Network Associates has a 30-day fully-functioning evaluation version of Virex 5.9.1. The Virex trial includes the application, not the control panel. Update the demo with current definitions: Sophos also has a 30-day evaluation, also fully-functioning, which includes the SWEEP application. The demo supports both English and Japanese. Intego has a limited-function French demo of Rival, "miniRival." Disinfector 1.0 is described by its author as shareware. However, it's strictly speaking a limited-runtime demo -- it stops functioning after 20 trial runs on one system. It's described as a beta release, but the author expects users to register it at a charge of $30 [subsequently reduced to $15]: in return, they get a version which can be used an unlimited number of times. It only detects a handful of Mac system viruses which the author claims that commercial vendors have not detected, and have not been reported in the wild. In the early days of virus/antivirus technology, a number of utilities were made available which addressed only one or a few viruses, and a proliferation of free AutoStart worm detectors continues that honourable tradition. However, charging for this particular utility puts it into the same arena as the commercial scanners which detect a far wider range of threats and for which full support is available, an area in which it cannot at present compete. Disinfector was briefly available at Info-Mac, but has since been removed.

There have also been a number of proposals since John Norstad announced the retirement of Disinfectant, suggesting that if the code was made public, it would be possible to maintain and further develop Disinfectant, possibly still as a freeware product. This is misguided, for a number of reasons.

8.4 Other freeware/shareware packages

For other freeware\shareware Mac packages, try Info-Mac mirrors like: The University of Texas holds some older documentation on Mac viruses. Tracker INIT and DelProtect INIT, both by Ioannis Galidakis, were first released on 19-Nov-98. Tracker is a behavior blocker something like the retired program GateKeeper. DelProtect protects against malicious file deletion. Tracker is now at version 1.1. Scanner 1.1x also by Ioannis Galidakis was released 15-Jan-99, and is a free, generic, heuristic 68k virus scanner for advanced Macintosh users. John Dalgliesh has created Agax, an extensible, free anti-virus program which replaces his program AntiGax, and uses plug-ins called "Additives." At this time, Agax will detect and try to clean only SevenDust, CODE 9811, and the AutoStart worms (the worm additive was in beta testing at the time of this writing). The author's Web page and documentation invite Mac programmers to contribute additives. The Exorcist, free from Laffey Computer Imaging, may give some (by one description, about 90%) protection from the SevenDust family. Gatekeeper was not a scanner, but a generic tool. It is no longer supported by its author, but is still available on some sites. It is probably not safe to use or rely on on modern systems, and I believe the author recommends that people don't attempt to use it, though I've been unable to contact him to get confirmation.

In January 1997 Padgett Peterson, author of the PC utility DiskSecure, released the first version of his MacroList macro detection tool, which has been tested by the author on Macs (System 7.5 on SE/30, IIci and PowerMac) as well as Windows PCs, using considerably more macro viruses than Microsoft seem to have heard of..... The MacroList template is accessed by a button in the standard toolbar. This is not a virus scanner, but allows disabling of automacros, listing of any macros found in the current document etc. Version 1.10 was due for release by the time of writing (February 1997), and an adaptation for Office97 is in progress. Watch the Web page for further details. [v1.1 and the Office 97 "late beta" were available as at 18th March 1997.] MacroList is freeware, but please be sure to read the TRIALS link.

WormGuard by Clarence Locke is a free on-access extension that affords AutoStart worm protection: The following free scanners may remove AutoStart 9805 and its B, C, D, E, and F variants and may be useful in the absence of a commercial application. There are a few reported instances of failures by some of these programs to identify or remove the AutoStart worms, and it is likely that D might be mis-identified as C, and E may be mis-identified as the original worm. [SL] As stated above, one-shot solutions to a very small subset of a particular class of threat have a long and honourable history, and are very welcome when a new threat catches the antivirus developers on the hop (it can take some time to incorporate detection of new threats into the product update cycle). NB The maintainer does not currently have the time or resources to do full detection testing of these products (or any other). [DH]

8.5 Commercial Packages

Commercial packages include NAV (Norton AntiVirus for Macintosh) [NAV supersedes SAM (Symantec Antivirus for Macintosh)], Virex for Macintosh, Rival, and Sophos Anti-Virus for Macintosh (SAV).

Virex, NAV, and SAM all address a full range of threats, including Trojans and macro viruses, and can do scheduled scanning as well as on-access (memory-resident) scanning.

++ Sophos Anti-Virus for Macintosh (SAV) was upgraded in January 1999 to include the SWEEP on-demand scanner. The shipping version can be downloaded for free evaluation. English and Japanese are supported.

Stand-alone on-access scanning is not yet available in the release version, but is now in beta. Server-based on-access scanning is already available for Mac clients on NT or NetWare networks.

The program offers customizable reporting and notification from an attractive interface. So far, compressed archives must be decompressed before scanning; I am assured that archive scanning will be in future versions. Complete documentation is in PDF format.

+ Sophos combines an intercept driver (InterCheck) and a scanner application (SWEEP). Sales are not retail, but direct or through the Sophos Distributor network. Free technical support is all-year round, any time of day. Virus identity updates are available from the Web between monthly CD-ROMs. Major developments in the Sophos product are expected, including smooth large-scale deployment and ease of updating over networks.[SL]

Norton AntiVirus for Macintosh (NAV) launched May 18, 1998. New features included LiveUpdate virus definition updates over the Internet, enhanced macro virus protection, automatic file repair, a bootable CD-ROM for emergencies, faster scanning for PPC, and a universal SafeZone.

NAV, SAM, and Virex offer checksumming/integrity checking (detecting possible infection by unknown viruses, by monitoring changes in infectable files) - the correct checksums or fingerprints for individual files are kept in a database file. All three applications check files compressed with StuffIt.

NAV, formerly SAM, is particularly oriented towards behaviour blocking: the Intercept tool can be configured to raise an alert at the slightest whiff of a 'suspicious' operation. Unfortunately, this can be counterproductive in real life, since an over-stringent alert policy is apt to result in the facility being turned off altogether. However, configuration is very flexible.

SAM (Symantec AntiVirus for Macintosh) support was discontinued May 1; the last update is for July '99. From Symantec's advice:

"In order to maintain the safety and security of your data from viruses without interruption, we recommend that you upgrade to NAVM 5.0.3 before May 1st. For presales and upgrade questions, please contact customer service. They can be reached at 800-441-7234 or online at:"
[SAM 4.5.x needs the 4.5->4.5.1 application patch to run current definitions, and the 4.5.3 Intercept patch to resolve a compatibility issue with Microsoft Office 98, and Segment Loader errors when Intercept loads. SAM application Minimum and Preferred memory allocations must be increased from their shipping defaults to 5000K or greater. The (May 1998) SAM definitions files included a Read Me with instructions. More information may be available from Symantec SAM support on the Web.]

Symantec issued a Norton AntiVirus 5.x->5.0.3 patch for Mac OS 8.5, fixing the problem with copying files on AppleShare networks.

Virex offers very fast scanning is easy to update, and includes checksumming for the detection of unknown viruses. It's also possible to buy an administration package. The basic package includes a control panel for scanning on file or diskette access which can be locked independently of the administration package. Installation and interface are easy and efficient. Virex 5.8 scans ZIP archives, has a contextual menu plug-in module, and interface enhancements.

Virex 5.9.1 was released on 18-Jan-99, for compatibility with Mac OS 8.5 and Virex Administrator 1.4, and can be downloaded.

Registered users who bought McAfee VirusScan during the past six months or so, and registered users of Virex 5.8 and 5.9 could still upgrade: Virex Administrator version 1.4 was released by NAI on 23-Dec-98. Virex and Virex Administrator had these home pages: ++ A new release is in beta.

Dr Solomon's Software acquired Virex and netOctopus from Datawatch Corp. on 10-Oct-97. Network Associates (NAI) acquired Dr Solomon's on 13-Aug-98. Netopia, Inc., acquired what is now named Timbuktu netOctopus in late '98 or early '99.

++ VirusScan 3.0.1 is the final version for Macintosh, and may be updated for macro viruses into 1999, but will never have AutoStart worm definitions or definitions for the new System viruses like SevenDust E. VirusScan customers need to take advantage of a free upgrade to Virex as soon as possible.

++ Dr. Solomon's for Macintosh went through various stages of neglect through late 1998 and support appears to have vanished altogether in 1999, when customers started to receive Virex disks instead of Dr. Solly's updates.

Rival 3.0.4 is available from Intego.

++ F-Secure for Macintosh is one of the best-kept secrets in anti-virus. The last time I saw it, it detected macro viruses only. You might be lucky and find some reference to it at:

8.6 Contact Details

Network Associates (for Virex, Dr Solomon's Anti-Virus Toolkit, and VirusScan) Dr. Solomon's Software Ltd. (for Dr. Solomon's Anti-Virus Toolkit) Symantec Corporation (for NAV and SAM) Intego (for Rival) Sophos Plc (for Sophos Anti-Virus) ++ Details on DataFellows will be included when I've determined the current status of F-Secure for Macintosh.

9.0 Welcome Datacomp

From time to time there are reports from Mac users that the message 'Welcome Datacomp' appears in their documents without having been typed. This is the result of using a Trojanised 3rd-party Mac-compatible keyboard with this 'joke' hard-coded into the keyboard ROM. It's not a virus - it cannot infect anything. The only cure is to replace the keyboard (be polite but firm with the dealer if you were sold this as a new keyboard!).

10.0 Hoaxes and myths

Some of these are PC-specific, rather than Mac-specific, while some have no basis in reality on any system. [I look forward to hearing about the first Turing machine infector....] They are included here (a) because Mac support staff are accustomed to being asked about them (b) because anything that might work on a real PC might also work with DOS emulation, in principle.

++ This section may vanish in the near future, or at least contract. The hoax business has changed a lot since this FAQ began.

10.1 Good Times virus

There is no Good Times virus that trashes your hard disk and launches your CPU into an nth-complexity binary loop when you read mail with "Good Times" in the Subject: field.

You can get a copy of the latest version of Les Jones' FAQ on the Good Times Hoax on the World Wide Web:

There's a Mini-FAQ available as:

10.2 Modems and Hardware viruses

There is no modem virus that spreads via an undocumented subcarrier - whatever that means.... There is no virus that causes damage to hardware.

10.3 Email viruses

Any file virus can be transmitted as an E-mail attachment. However, the virus code has to be executed before it actually infects. Sensibly configured mailers and browsers don't allow this: check yours. In particular, check that your Web browser doesn't automatically pass Word documents to Word 6 to open, since this may result in embedded macros being launched.

10.4 JPEG/GIF viruses

There is no known way in which a virus could sensibly be spread by a graphics file such as a JPEG or .GIF file, which does not contain executable code. Macro viruses work because the files to which they are attached are not 'pure' data files.

10.5 Hoaxes Help

If you should receive a virus warning, look at these sites before forwarding it along (in fact, it's probably never justified to pass on a virus alert indiscriminately, and reputable antivirus companies don't do this. In fact, the information that such and such a virus exists is not, in itself, useful to the average computer user, even if it does. A statement like, "Please forward to everyone!" is one mark of a hoax. Corporates who haven't sorted out their hoax management strategy might get some mileage out of my mini-paper on "Dealing with Internet Hoaxes", though it's getting a bit long in the tooth. It is, however, one of the few papers on the subject which deals with it from an adminstrator's/manager's point of view as well as from an everyday user/victim's. [DH] I'm slightly surprised to find that I'm managing an EICAR project in this area: watch this space.

11.0 Glossary

12.0 General Reference Section


12.1 Mac Newsgroups

The focus on these two groups tends to be IBM-compatible, but Mac issues are certainly aired. Alt.comp.virus is unmoderated, and the quality of the advice and opinions aired there is very variable - there are many reputable and expert posters, and many mischievous and misleading contributions. Caveat lector.... comp.virus lies dormant for years at a time, but is well worth watching when there's anything there.

12.2 References and Publications

13.0 Mac troubleshooting

Since the initial release of this document, a number of people have E-mailed me asking for help with a possibly virus-related problem. While I'll always help if I can, I should point out (1) I'm an experienced Mac user and an IT support professional, but I don't claim to be a Mac expert (2) pressure of work and other commitments and a huge E-mail turnover means that I can't promise a quick or in-depth response [DH]. Whether you mail direct or post to a relevant newsgroup, it's helpful if you can supply a few details, such as: Here are a few steps that it might be appropriate to try if virus scanning with an up-to-date scanner finds nothing. This section will be improved when and if I have time.

Rebuilding the desktop is by no means a cure-all, but rarely does any harm. It may be worth disabling extensions when you do this, especially if the operation doesn't seem to be completed successfully.

To disable extensions, restart the machine with the shift key held down until you see an Extensions Off message. If you're rebuilding the desktop, release the shift key and hold down Command (the key with the Apple outline icon) & Options (alt) until requested to confirm that you want to rebuild.

Disabling extensions is also a good starting point for tracking down an extensions conflict. If booting without extensions appears to bypass the problem, try removing extensions with Extensions Manager (System 7.5) - remove one at a time, and replace it before removing the next one and booting with that one removed. Remember that if removing one stops the problem, it's still worth putting it back and trying all the others to see if you can find one it's conflicting with. Extensions Manager also lets you disable control panels. If you don't have Extensions Manager, try Now Utilities or Conflict Catcher.

Parameter RAM (PRAM) contains system information, notably the settings for a number of system control panels. 'Zapping' PRAM returns possibly corrupt PRAM data to default values. A likely symptom of corrupted PRAM is a problem with date and time (but could be a symptom of a corrupted system file). With system 7, hold down Command-Option-P-R at bootup until the Mac beeps and restarts. You may have restore changes to some control panels before your system works properly. If the reset values aren't retained, the battery may need replacing.

End "Viruses and the Macintosh" version 1.6 by David Harley

Last Modified September 12, 1999