Summary

This virus spreads only under Linux operating system, infecting Elf-style executables. Found in the fall of 1996, Staog is the first known Linux virus.

Staog is written in assembler. It attempts to stay resident and infect binaries as they are executed by any user. Stoag tries to subvert root access via three known vulnerabilities (mount buffer overflow, tip buffer overflow and one suidperl bug).

Additional Details

Staog contains several text strings, including:

        Staog by Quantum / VLAD
        /dev/kmemx/etc/mtab~
        /sbin/mount
        /tmp/t.dip
        /bin/sh
        /sbin/dip /tmp/t.dip
        chatkey
        /tmp/hs
        #!/bin/sh\nchmod 666 /dev/kmem\n/tmp/hs
        #!/usr/bin/suidperl -U\n$ENV{PATH}=\"/bin:/usr/bin\";
        \n$>=0;$<=0;\nexec(\"chmod 666 /dev/kmem\");\n

VLAD is an Australian virus group, which also wrote the first Windows 95 virus, Boza.

Staog can be detected by searching all binaries for the following hex search string:

        215B31C966B9FF0131C0884309884314B00FCD80

Staog is not known to be in the wild at the time of this writing (February 1997).

[Analysis: Mikko Hypponen, F-Secure]