Summary

Mimail.C worm was first found on 31st of October, 2003. The worm spreads in e-mails as a ZIP archive that contains the worm's executable with PHOTOS.JPG.EXE name. The worm tries to perform a DoS (Denial of Service) attack on certain sites and to steal information from infected computer users.

Additional Details

Shortly after Mimail.C was found, also D, E, F, G and H variants have been found. They have minor differences and attack other web sites. F-Secure Anti-Virus detects them too.

Descriptions of these Mimail variants can be found here:

Mimail.D: http://www.europe.f-secure.com/v-descs/mimail_d.shtml

Mimail.E: http://www.europe.f-secure.com/v-descs/mimail_e.shtml

Mimail.F: http://www.europe.f-secure.com/v-descs/mimail_f.shtml

Mimail.G: http://www.europe.f-secure.com/v-descs/mimail_g.shtml

Mimail.H: http://www.europe.f-secure.com/v-descs/mimail_h.shtml The worm's file is a PE executable 12832 bytes long packed with UPX file compressor. The unpacked file's size is 28192 bytes.

Installation to system

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 NETWATCH.EXE file to Windows directory and creates a startup key for this file in System Registry:

 [HKLM\Software\Microsoft\Windows\CurrentVersion\Run]
 "NetWatch32" = "%windir%\netwatch.exe"

where %windir% is Windows directory name.

Then the worm deletes the following files from Windows folder if they are present:

 zip.tmp
 exe.tmp
 eml.tmp

After that the worm copies its file to Windows directory as EXE.TMP and creates a ZIP archive with the name ZIP.TMP. This ZIP archive contains the worm's copy with PHOTOS.JPG.EXE name.

The worm activates its payload and spreading theads if it can resolve the 'www.google.com' address.

Spreading in e-mails

The worm spreads in e-mails as a ZIP archive that contains the worm's executable with the PHOTOS.JPG.EXE name. The worm fakes the sender's e-mail address by composing it from 'james@' and the domain name of a recipient. An infected message looks like that:

From:

 james@recipient_domain_name

Subject:

 Re[2]: our private photos    <some random characters>

Body:

 Hello Dear!,

 Finally i've found possibility to right u, my lovely girl :)
 All our photos which i've made at the beach (even when u're without ur bh:))
 photos are great! This evening i'll come and we'll make the best SEX :)

 Right now enjoy the photos.
 Kiss, James.
 <some random characters>

Attachment:

 photos.zip

The worm does not use any exploits to make its file start automatically on a recipient's system. The worm will infect a recipient's computer only when he/she unpacks the executable file from the archive and runs it.

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 addresses are saved into the EML.TMP file located in Windows directory.

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

The worm tries to perform a DoS (Denial of Service) attack on the following sites:

 darkprofits.com
 darkprofits.net
 www.darkprofits.com
 www.darkprofits.net

If the worm is widespread these sites may go down due to huge traffic amount generated by the worm.

Additionally the worm checks foreground windows and if it locates a window belonging to the certain application, the worm collects certain information from it and saves it to C:\TMPE.TMP file. Then this file is sent to e-mail addresses that are stored in an encrypted form in the worm's body.

NOTE

Mimail.C was distributed in an Inor variant. Inor is a VBS script that simply drops and runs a binary in c:\mware.exe (Mimail.C). The distributed VBS arrives in email messages with:

Subject:

 This is the Postfix program at host prodigy.com
 I'm sorry to have to inform you that the message returned
 below could not be delivered to one or more destinations.

 The message itself and all the other important information
 are included into the attachment.

Attachment:

 undelivered.hta

Detection

Detection in F-Secure Anti-Virus was published on October 31st, 2003 in the following updates:

[FSAV_Database_Version]

Version=2003-10-31_01

Technical Details: Alexey Podrezov and Katrin Tocheva; October 31st-November 3rd, 2003;

F-Secure Corporation