Analysis by: Anthony Joe Melgarejo
ALIASES:

Trojan.Backdoor (Symantec)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This backdoor may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 32,256 bytes
File Type: DLL
Memory Resident: No
Initial Samples Received Date: 22 Mar 2013

Arrival Details

This backdoor may be dropped by the following malware:

  • TSPY_INJECTO.KRS

Installation

This backdoor drops and executes the following files:

  • %User Temp%\w7e{random alphanumeric characters}.tmp - also detected as BKDR_AGENT.KSI

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

NOTES:
It bypasses UAC (User Account Control) and executes %User Temp%\w7e89.tmp (detected as TSPY_INJECTO.KRS). Thus, malicious behavior is exhibited in the system.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.818.03
FIRST VSAPI PATTERN DATE: 22 Mar 2013
VSAPI OPR PATTERN File: 9.819.00
VSAPI OPR PATTERN Date: 23 Mar 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Remove the malware/grayware file that dropped/downloaded BKDR_AGENT.KSI

    • TSPY_INJECTO.KRS

Step 3

Scan your computer with your Trend Micro product to delete files detected as BKDR_AGENT.KSI. 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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