Threat Description

Fbound

Details

Aliases: Fbound, W32/Impat.A-mm, I-Worm.Zircon
Category: Malware
Type:
Platform: W32

Summary


Fbound is a mass-mailer that was first discovered in March, 2002.



Removal


The worm doesn't install itself to system. So to remove the worm it's enough to restart an infected computer. After that you can delete the worm's file from temporary folder where it was dropped by e-mail cliend upon attachment execution.



Technical Details



Variant:Fbound.C

The Fbound.C variant of the worm appeared in the wild on March 14th 2002.

When activated, the worm first gets user's SMTP server and e-mail address. Then it gets Windows Address Book location, loads up virus exe to memory, encodes it with Base64 encoding, searches WAB file for e-mail addresses and sends itself to all these addresses. The infected e-mail looks like this:

Subject:      Important  Attachment:   patch.exe  

The message body is empty. When the recipient's address contains '.jp' (Japan) in the end, the subject line is randomly chosen from the list of 16 different subjects.

It should be noted that the worm encodes its file into a single line and this violates RFC regulations for Base64 encoding. So some e-mail servers will not process worm's messages.



Detection


Detection of Fbound worm is available with the updates published on 14th of March 2002.



Technical Details:Gergely Erdelyi, Katrin Tocheva; Sami Rautiainen; F-Secure Corp.; March 14th, 2002


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