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BKDR_BLOHI.GB

July 19, 2013
 Analysis by: Kerstan Josef Navarro
 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:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  TECHNICAL DETAILS

File Size:

234853 bytes

Memory Resident:

Yes

Initial Samples Received Date:

18 Jul 2013

Installation

This backdoor drops the following files:

  • %System%\mswinsck.ocx

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It drops and executes the following files:

  • %System%\{random file name}.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This backdoor 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} = "%System%\{random file name}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random} = "%System%\{random file name}.exe"

Download Routine

This backdoor connects to the following URL(s) to download its component file(s):

  • http://{BLOCKED}5.{BLOCKED}s.com/pds/201304/27/64/mswinsck.ocx

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.158.06

FIRST VSAPI PATTERN DATE:

16 Jul 2013

VSAPI OPR PATTERN File:

10.159.00

VSAPI OPR PATTERN Date:

16 Jul 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

Scan your computer with your Trend Micro product and note files detected as BKDR_BLOHI.GB

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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} = "%System%\{random file name}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • {random} = "%System%\{random file name}.exe"

Step 5

Search and delete this file

[ Learn More ]
There may be some 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.
  • %System%\{random file name}.exe
  • %System%\mswinsck.ocx

Step 6

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