Analysis by: Michael Cabel
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003, Windows Vista, Windows 7

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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 deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 39,424 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 08 Dec 2011

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 drops the following copies of itself into the affected system:

  • %System Root%\Documents and Settings\All Users\Local Settings\Temp\{Random File Name}.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{Random Numbers} = "%System Root%\Documents and Settings\All Users\Local Settings\Temp\{Random File Name}.exe"

Other Details

This Trojan deletes the initially executed copy of itself

NOTES:

For Windows 7 and Windows Vista:

It adds the following copy of itself:

  • %User Temp%\{Random File Name}.exe

It modifies the following registry entry ro enable its automatic execution in every system startup:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
Load = "%User Temp%\{Random File Name}.exe"

(Note: Default value for this registry entry is "").

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.636.01
FIRST VSAPI PATTERN DATE: 10 Dec 2011
VSAPI OPR PATTERN File: 8.637.00
VSAPI OPR PATTERN Date: 11 Dec 2011

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

Scan your computer with your Trend Micro product and note files detected as TROJ_AGENT.BASB

Step 3

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {Random Numbers} = "%System Root%\Documents and Settings\All Users\Local Settings\Temp\{Random File Name}.exe"

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • From: Load = "%User Temp%\{Random File Name}.exe"
      To: Load = ""

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_AGENT.BASB. 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.


Did this description help? Tell us how we did.