Type File virus
Date Discovered 1988.06
Place of Origin
Source Language
Platform MacOS
File Type(s)
Infection Length 712 bytes
Reported Costs

Init29 is a virus for the Macintosh. It was particularly virulent shortly after the time it appeared and had one variant appear nearly five years after the release of the original.


Init29 is activated when an infected application is run or even selected. The system file is infected, and the virus patches the Open resource file trap. The virus will infect the resource forks of all files on the system, including documents and data, though it will only be able to spread through application files.

For applications, it will add itself in the form of a 712 byte code resource numbered with the lowest free code resource number and an INIT 29 to other files. Any action that causes the resource fork to be called will cause it to be infected. Applications do not need to be launched in order to be infected.

The virus is not intentionally malicious, however it may cause severe disruption to the system. It occasionally damaged applications it infected causing them to run incorrectly. It will infect files that have already been infected, causing them to grow too large for the memory or disk space if left unchecked. The user will encounter "out of memory" errors when trying to run these files.

When a locked floppy disk is place in an infected computer, it will display a message: "The disk [volume name] needs minor repairs. Do you want to repair it?"


In early spring of 1994 (six years after the original) the Init29.B variant appeared on the west coast of the United States. It is mostly similar to the original.


Symantec, Init 29A. 2007.02.13

Sophos Antivirus, Mac/Init-29. 2001.20.02

New Macintosh Virus Discovered. 1994.04

David.J.Ferbrache. Mac Digest, List of known Macintosh viruses. 1989.05.11

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