Neil Schemenauer's Web Log


August 19, 2003

Filtering W32.Sobig.F

We are receiving a lot of junk mail on our server, sent by people infected with the W32.Sobig.F worm/trogin. We are rejecting message based on headers. Here's the list of subject headers that I have seen used so far:

Re: Thank you!
Thank you!
Re: Details
Your details
Re: Re: My details
Re: Approved
Re: Re: Approved
Re: Your application
Re: Wicked screensaver
Re: That movie

The virus also seems to always set the following headers:

X-MailScanner: Found to be clean
Importance: Normal
X-Mailer: Microsoft Outlook Express 6.00.2600.0000
X-MSMail-Priority: Normal
X-Priority: 3 (Normal)
MIME-Version: 1.0

Filtering based on Subject, X-MailScanner and X-Mailer seems pretty effective. Right now our server is rejecting a few of these messages a minute. Now, if only people would stop using broken virus scanners that send out useless messages the following:

Subject: Virus Alert

The mail attachment file email-body was blocked, according to
InterScan VirusWall's configuration. The action blocked was taken.

So many monkeys out there.