Analysis by: JessaD

 ALIASES:

TrojanDownloader:Win32/Waledac.C (Microsoft); W32/Nuwar.gen.b@mm (McAfee)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan may be downloaded from several remote sites. It may also be downloaded from links in email messages sent out by WORM_KELIHOS.SM.

It connects to website to download and execute a malicious file detected by Trend Micro as WORM_KELIHOS.SM.

This Trojan executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 19,968 bytes
Memory Resident: No
Initial Samples Received Date: 05 Jan 2011
Payload: Downloads files

Arrival Details

This Trojan may be downloaded from the following remote site(s):

  • http://{BLOCKED}i.com/install_flash_player.exe
  • http://{BLOCKED}p.com/install_flash_player.exe
  • http://{BLOCKED}cu.com/install_flash_player.exe
  • http://{BLOCKED}r.com/install_flash_player.exe
  • http://{BLOCKED}de.com/install_flash_player.exe

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://{BLOCKED}.{BLOCKED}.240.36/flash2.exe

It saves the files it downloads using the following names:

  • %Windows%\Temp\_ex-{random numbers}.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

Trend Micro detects the dowloaded file as:

  • WORM_KELIHOS.SM

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

NOTES:
This malware may be downloaded from links in email messages sent out by WORM_KELIHOS.SM

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: 7.750.01
VSAPI PATTERN Date: 05 Jan 2011
VSAPI PATTERN Date: 1/5/2011 12:00:00 AM
VSAPI OPR PATTERN File: 7.751.00
VSAPI OPR PATTERN Date: 06 Jan 2011

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by TROJ_KELIHOS.DLR

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_KELIHOS.DLR. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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