BKDR_AGENT.SMOL

October 10, 2012
 ALIASES:

Trojan:Win32/Scar.G (Microsoft); Downloader-CKA (McAfee); Trojan.Gen (Symantec); Trojan.Win32.Scar.g (v) (Sunbelt); Trojan.Generic.KD.23424 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

  TECHNICAL DETAILS

File Size:

69,858 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

22 Sep 2012

Arrival Details

This backdoor 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 backdoor creates the following folders:

  • %User Temp%\d61fe900-5285-4879-bb37-b85d0f65f9b5

(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.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Cryptography

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Cryptography
MachineGuid = "d61fe900-5285-4879-bb37-b85d0f65f9b5"

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\d61fe900-5285-4879-bb37-b85d0f65f9b5\wrk1.tmp_46

(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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

Delete this registry key

[ 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_CURRENT_USER\SOFTWARE\Microsoft
    • Cryptography

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_CURRENT_USER\Software\Microsoft\Cryptography
    • MachineGuid = "d61fe900-5285-4879-bb37-b85d0f65f9b5"

Step 4

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.
  • %User Temp%\d61fe900-5285-4879-bb37-b85d0f65f9b5\wrk1.tmp_46

Step 5

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\d61fe900-5285-4879-bb37-b85d0f65f9b5

Step 6

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