Summary

Mimail.F worm was found on 2nd of November, 2003. It is a close variant of Mimail.C worm. The description of Mimail.C worm variant can be found here:

http://www.europe.f-secure.com/v-descs/mimail_c.shtml

Additional Details

The Mimail.F worm is a minor variant of Mimail.C worm. The differences between these 2 versions are as follows:

1. The Mimail.F worm's file is 10784 bytes long, compressed with UPX file compressor, the unpacked file's size is 23072 bytes.

2. The worm installs itself to Windows folder as CNFRM.EXE file and creates a startup key in the Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run] "Cnfrm32" = "%windir\cnfrm.exe"
where %windir% is a Windows directory name.

3. The worm performs a DoS (Denial of Service) attack on the following sites:

fethard.biz fethard-finance.com www.fethard.biz www.fethard-finance.com
4. The worm spreads itself in the following message:

From: john@<domain of the recipient>
Subject: don't be late! <some random characters>
Body: Will meet tonight as we agreed, because on Wednesday I don't think I'll make it,
so don't be late. And yes, by the way here is the file you asked for. It's all written there. See you.
<some random characters>
Attachment: readnow.zip
The attachment is a ZIP archive that contains the worm's executable file with READNOW.DOC.SCR name.

5. The .F worm variant doesn't have the spying functionality that was present in the .C worm variant.

Detection

Detection in F-Secure Anti-Virus was published on November 3rd, 2003 in the following updates:

[FSAV_Database_Version]
Version=2003-11-03_01

Technical Details: Alexey Podrezov, November 3rd, 2003;