Rash of New IM Worms

Several new Instant Messenger (IM) worms were discovered by antivirus vendors on March 6th and 7th. Of these, six are variants of the Kelvir IM worm which intend to download variants of the SDbot Trojan - allowing malicious remote access to compromised systems. Also debuting was the Crog IM worm which has a payload that shuts down security software, redirects attempts to access security websites, and lowers the security settings of the compromised PC by modifying various Registry keys.
Kelvir.A, Kelvir.B, Kelvir.C descriptions
Crog worm description