BKDR_OBFUSCA.HHZ

October 09, 2012
 Analysis by: Cris Nowell Pantanilla
 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.

It injects its dropped file/component to specific processes.

  TECHNICAL DETAILS

File Size:

6,887,424 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

11 Aug 2011

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 drops the following file(s)/component(s):

  • %User Temp%\autoexec.bat
  • {folder where malware is dropped or executed}\110805_Î–ûEÎ’YEz•¨ŽQlŽ‘—¿W\110805_Î–ûEÎ’YEz•¨ŽQlŽ‘—¿W.ppt
  • %User Temp%\tabcteng.dll

(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 creates the following folders:

  • {folder where malware is dropped or executed}\110805_Î–ûEÎ’YEz•¨ŽQlŽ‘—¿

It injects its dropped file/component to the following processes:

  • IEXPLORE.EXE

Autostart Technique

This backdoor modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Netman\Parameters
ServiceDll = "%User Temp%\tabcteng.dll"

(Note: The default value data of the said registry entry is %SystemRoot%\System32\netman.dll.)

Other System Modifications

This backdoor modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Netman
Start = "2"

(Note: The default value data of the said registry entry is 3.)

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.348.05

FIRST VSAPI PATTERN DATE:

11 Aug 2011

VSAPI OPR PATTERN File:

8.349.00

VSAPI OPR PATTERN Date:

11 Aug 2011

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

Restart in Safe Mode

[ Learn More ]

Step 3

Restore this modified 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\SYSTEM\CurrentControlSet\Services\Netman
    • From: Start = "2"
      To: Start = "3"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netman\Parameters
    • From: ServiceDll = "%User Temp%\tabcteng.dll"
      To: ServiceDll = "%SystemRoot%\System32\netman.dll"

Step 4

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.
  • {folder where malware is dropped or executed}\110805_Î–ûEÎ’YEz•¨ŽQlŽ‘—¿

Step 5

Search and delete these files

[ 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%\autoexec.bat
  • %User Temp%\tabcteng.dll

Step 6

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