Summary

Mimail.S belongs to the Mimail mass-mailing worm family. It was first found on 29th of January, 2004. Like previous versions, the worm attempts to steal credit card information from users by asking them to fill a fake Microsoft registration form.

Additional Details

System Infection

When the worm's file is run, it registers itself as a service process and becomes invisible in Task List on Windows 9x systems.

The the worm copies itself as "rabbit.exe" file to Windows directory and creates a startup key for this file in System Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run] "RabbitWannaHome" = "%windir%\rabbit.exe"
where %windir% is Windows directory name.

Another copy is placed to the Windows Directory with the name 'x' which is used later when the worm sends itself in infected emails.

The worm activates the following functions only if it can resolve 'www.google.com' address i.e. when connection to Internet is available.

E-Mail Propagation

When spreading through email this variant of the worm composes e-mail form a list of text strings within its body.

The name of the attachment is composed as follows, the first part of the filename is chosen from:

my priv private prv the best super great cool wild s*x f*ck
With a separator selected from:

_ (underscore) - (dash) __ (double underscore)
Followed by a second word, form the list:

pic img phot photos pctrs images imgs scene plp act action
The extension of the attachment if chosen from the following list:

.pif .scr .exe .jpg.scr .jpg.pif .jpg.exe .gif.exe .gif.pif .gif.scr


To collect victim's e-mail addresses the worm scans all files on a hard drive except those with the following extensions:

bmp jpg gif exe dll avi mpg mp3 vxd ocx psd tif zip rar pdf cab wav com
The collected e-mail addresses are saved into "outlook.cfg" file located in Windows folder.

To send e-mails the worm tries to contact the recipient's SMTP server directly. For this purpose it tries to resolve the current user's DNS server and search for SMTP server info for recipient's domain.

Payload

After startup the worm asks the user to fill a fake Microsoft registration form. Information from that form is saved to a file and is sent to the worm's author.



The collected data is saved to a file named "xx" that is located in the root of C: drive. After the user has entered the credit card information Mimail.S sends it to predefined email addresses.

Detection

Detection for Mimail.S is available in the following FSAV updates:

[FSAV_Database_Version]
Version=2004-01-29_01

Technical Details: Gergely Erdelyi and Ero Carrera; January 29th, 2004;