Analysis by: Abraham Latimer Camba


Exp/20121875-A (Sophos); Exploit.JS.CVE-2012-1875.a (Kaspersky); Exploit:JS/ShellCode.AV (Microsoft)


Windows 2000, Windows XP, Windows Server 2003


  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes


Infection Channel: Downloaded from the Internet

This malware exploits a vulnerability in CVE-2012-1875, which is addressed in MS12-037 bulletin.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

Once this malware exploits the vulnerability, it downloads malicious files.

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


File Size: Varies
File Type: HTML, HTM
Initial Samples Received Date: 13 Jun 2012
Payload: Downloads files

Arrival Details

This Trojan may be downloaded from the following remote sites:

  • http://{BLOCKED}.{BLOCKED}.241.239/css.htm

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}.{BLOCKED}.241.239/javaw.exe - detected by Trend Micro as BKDR_AGENT.BCSG
  • http://{BLOCKED}.{BLOCKED}.236.143/english/cala.exe - detected by Trend Micro as TROJ_AGENT.BCSH

It takes advantage of the following software vulnerabilities to download possibly malicious files:

It saves the files it downloads using the following names:

  • %User Temp%\log.gif

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.)

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


Minimum Scan Engine: 9.200
VSAPI OPR PATTERN File: 9.205.00
VSAPI OPR PATTERN Date: 20 Jun 2012

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 JS_DLOADER.SMGA

Step 3

Close all opened browser windows

Step 4

Scan your computer with your Trend Micro product to delete files detected as JS_DLOADER.SMGA. 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.

Step 5

Download and apply this security patch Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.

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