Analysis by: Mark Joseph Manahan
ALIASES:

TrojanDownloader:Win32/Karagany.I (Microsoft), PWS-Zbot.gen.ajy (McAfee), a variant of Win32/Injector.USA trojan (Eset)

 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 arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 20,992 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 10 Aug 2012

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This Trojan injects itself into the following processes running in the affected system's memory:

  • explorer.exe

Download Routine

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

  • http://{BLOCKED}orus-forum.com/752818.html

It saves the files it downloads using the following names:

  • %User Temp%\{random name}.tmp

(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.

As of this writing, the said sites are inaccessible.

NOTES:

The file downloaded is executed through the following command:

  • regsvr32 -s %User Temp%\{random name}.tmp

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.314.02
FIRST VSAPI PATTERN DATE: 10 Aug 2012
VSAPI OPR PATTERN File: 9.315.00
VSAPI OPR PATTERN Date: 11 Aug 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

Scan your computer with your Trend Micro product and note files detected as TROJ_KARAGANY.JV

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete the file detected as TROJ_KARAGANY.JV

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_KARAGANY.JV. 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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