Here is part of what McAfee says on it:
www.mcafee.com/anti-virus/
W32/Sobig.e@MM Medium 6/25/2003

http://vil.mcafee.com/dispVirus.asp?virus_k=100429

-- Update June 25, 2003 --
This threat was upgraded to a Medium risk due to an increase in prevalence over the past few hours.

This variant is similar to W32/Sobig.d@MM. The worm propagates via email and over network shares. It contains its own SMTP engine for constructing outgoing messages. The virus is sent in a ZIP archive, allowing it to bypass extension blocking rules. However, this requires the end user to perform extra steps in order to actually execute the virus.

The worm may arrive in an email with the following characteristics:
Body: Please see the attached zip file for details.
Attachment: your_details.zip (which contains details.pif)
* Note: This variant spoofs, or forges, the from address. Therefore the perceived sender is likely not a pointer to the infected user.