Hi Guys..
As per my usual Heads up.. only Higher risk Threats are listed here.. ie Symantec's Cat 2 or higher..

Symantec Info Page

W32.Simic.Worm

This ones entry is due to its Distribution Capability.

Threat Assesment
Wild:- Low
Damage:- Low
Distribution:- High

W32.Simic.Worm is a worm that uses MSN Messenger to spread itself to new victims.

Also Known As: I-Worm.Sinmsn [KAV]
Type: Worm
Infection Length: multiple files
Systems Affected: Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Me
Systems Not Affected: Windows 3.x, Macintosh, OS/2, UNIX, Linux
Technical Details
msn.exe will then check if MSN Messenger is running and if so will send sins.exe to whom ever contacts the victim.

Note
sins.exe can also have the name msninst.exe



Cheers