Weekly Report on Viruses and Intrusions – Bobax.D and Korgo A/B Variants

This week’s report on viruses and intrusions will deal with three worms: Bobax.D and the variants A and B of Korgo.

The D variant of the Bobax worm spreads via the Internet by exploiting the security holes mentioned below in those computers that have not been properly patched:

– RPC DCOM vulnerability, critical for Windows 2003/XP/2000/NT operating systems.

– LSASS vulnerability. When it exploits the LSASS vulnerability, Bobax.D can only affect and spread automatically to Windows XP/2000 computers that have port 5000 open. However, computers with other Windows operating systems can also be a source of transmission when a malicious user runs the file containing the worm in any of these computers.

Bobax.D carries out the following actions: it restarts the affected computers and opens several random ports through which a remote user can use the affected computer as an SMTP mail server in order to send spam.

The other two worms in this report are Korgo.A and Korgo.B, which like Bobax.D, spread via the Internet by exploiting the LSASS vulnerability.

These two worms open and listen on the TCP ports 113, 3067 and 2041. In addition, both worms attempt to connect to different IRC servers through port 6667 and they are designed to prevent the system from shutting down. Korgo.A and Korgo.B are 10,240 bytes in size when compressed with UPX v1.24, and 16,896 bytes in size once decompressed.