Name :	Gurong.A
Category:	Malware
Type:	Email-Worm, Worm
Platform:	Win32
Origin:	RUSSIAN FEDERATION
Date of Discovery:	March 21, 2006

The Gurong.A worm appeared on the 21st of March 2006. This worm spreads in e-mails and in Kazaa shared folders. It has a rootkit functionality.

Detection and Disinfection of Rootkits

If the rootkit is not detected or it is hidden, in order that the FSAV cannot detect its file, it is still possible to detect the malicious activity by scanning the system with a generic rootkit scanner, such as F-Secure BlackLight. More information about F-Secure BlackLight Rootkit Elimination Technology can be found here:

http://www.f-secure.com/blacklight/

The BlackLight utility is also able to disinfect computers that are infected by rootkits.

Installation to system

After the worm's file is run, it copies itself to the Windows System folder as wmedia16.exe and creates a startup key value for this file in the Registry:

[HKLM\Software\Microsoft\Windows\CurrentVersion\Run]
"WMedia16" = "%WinSysDir%\wmedia16.exe"

where "%WinSysDir% represents the Windows System folder.

Rootkit Hiding Techniques

The worm is able to hide the following items:
When the worm is active, it hides its own process, file and launch point in the registry.

The worm installs a call gate through \Device\PhysicalMemory to execute part of its code in kernel mode (ring 0). The kernel-mode code replaces the following function pointers from the system service table:
This allows it to hide files, registry keys and values. In addition, the worm is able to modify kernel-mode process structures to hide any process it specifies.

Spreading in e-mails

Before spreading, the worm looks for e-mail addresses in the victim's Windows Address Book (WAB) file and also in files with the following extensions:


The worm ignores e-mail addresses that contains any of the following substrings:


The subject of an infected message can be one of the following:


The body text of an infected message can be one of the following:


The infected attachment name can be any of the following:


Infected attachments can have the following extensions:


The worm spoofs (fakes) the sender's e-mail address. The following user names are used to compose the fake sender's address:

The following domain names are used to compose the fake sender's address:


Spreading to Kazaa shared folders

The worm copies itself to Kazaa (peer-to-peer client) shared folder with the following names:


The extensions of the copied files are randomly selected from the following variants: