Summary

The 'Fuzzynut' is a trojan written in Visual Basic. In order to run the trojan needs a Visual Basic run-time library VBRUN300.DLL that most of Windows users have in their \Windows\System\ directory. On every execution the trojan does the following:

1. Creates random number of folders with random names in C:\Windows directory. Names are generated by a special subroutine and have ASCII letters from 'a' to 'z' only.

2. Copies itself to root Windows directory as FUZZUNUT.EXE file.

3. Modifies WIN.INI 'run=' setting to 'run=fuzzynut.exe'. This allows the trojan to be run on each Windows bootup.

4. Changes registration entry for WinZip in WIN.INI as follows:

    [WinZip]
    win32_version=6.3
    Name=MyPantsFellOff
    SN=F12D235B

Surprisingly, this seems to be a valid WinZip registration key.

5. Changes volume label on C: drive to 'LICKMYBALLS'.

The trojan was fake-posted to alt.comp.virus newsgroup by someone (trojan author most likely) using the name of Nick Fitzgerald. Nick Fitzgerald is the editor of the Virus Bulletin magazine and has nothing to do with the trojan.

[Analysis: Alexey Podrezov, F-Secure]