Trojan-Spy:W32/Goldun.CW

Trojan-Spy:W32/Goldun.CW silently downloads and installs a file on the infected system. The downloaded file in turn downloads and executes another file which is most likely malware.

Arrival

Goldun.CW is distributed as an FSG packed EXE file. It creates and opens the following Bitmap file to hide its original intent:

Note: This image is saved in the default Temporary folder as screen.bmp.

Execution

Goldun.CW drops the following UPX-compressed DLL file on Windows System folder:

• %systemdir%\mscods.dll

Note: %systemdir% by default is C:\Windows\system32.The DLL will connect, download, and execute a file from the following URL:

• http://everythingdiscounted.biz/store/images/extras/[...].jpg

The code containing the above URL is encrypted using a simple XOR routine.The executed file drops a file named vbrs.bat into the default Temporary folder. The BAT file deletes the EXE file and the BAT file itself, effectively removing all traces of the malware on the system.

Registry

The DLL file is installed as a Browser Helper Object (BHO) so that when ever an Internet Explorer session is started, the DLL will also execute. It does this by creating the following Registry keys:

• [HKCR\CLSID\{45357971-2534-8760-3685-423479197575}]
• [HKLM\SOFTWARE\Classes\CLSID\{45357971-2534-8760-3685-423479197575}]