Summary

Mabutu is a mass-mailing worm which spreads in short and simple emails with infected attachments.

Mabutu comes with an IRC-controlled backdoor component.

Additional Details

Mabutu arrives in a UPX-packed dropper with the main component as a DLL inside. The main DLL is 49152 bytes in size and is not packed.

System Infection

Upon execution Mabutu copies itself to the Windows Directory as <random character>TWAIN.EXE and drops a DLL, which is the body, as <random character>TWAIN.DLL. The DLL file is added to the registry as

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run] "winupdt" = "%WindowsDir%\RUNDLL32.EXE <random character>TWAIN.DLL,_mainRD"
%WindowsDir% represents the Windows folder name, for example C:\Windows on Windows XP systems.

Mabutu keeps its configuration data in an scrambled data file called cfg.dat in the Windows Directory.

Email Propagation

Mabutu collects email addresses from various places. It checks Windows Address Book, MSN Messenger Buddy list, Outlook Express mailboxes and files with the following extensions: .WAB, .HTM, .HTML, .TXT

Using its own SMTP engine Mabutu sends infected messages to the collected addresses.

Subject is one of:

Hi Hello Important Hello I'm in love Sex Wet girls I'm nude Fetishes gutted Ok cunt
Attachment names:

britney jenifer photo creme_de_gruyere
with extensions .{JPG|TXT}<lots of spaces>.SCR or .ZIP.

The message body is either a file path, collected from Kazaa Shared Folder and My Document folders, or one of the following strings:

the_details the_document the_message
The mailing routine tests if there is connection to the Internet by connecting to www.google.com. If the user has a screen saver the worm waits until it starts then it activates its mass-mailing code.

Payload

The payload in Mabutu is an IRC-controlled backdoor. The backdoor connects to one of the many predefined IRC servers and after joining a channel it awaits for commands from its creator. Using these commands the attacker can get information from the worm (eg. number of sent infected emails, OS version, etc) and remotely start the mass-mailing routine.

Mabutu has the capability to update itself by downloading and activating a DLL from a predefined web location.

Detection

Detection for this malware was published on July 27th, 2004 in the following F-Secure Anti-Virus updates:

[FSAV_Database_Version]
Version=2004-07-27_01



Write-up: Katrin Tocheva, July 29th, 2004;

Technical Details: Gergely Erdelyi, July 29th, 2004;