Analysis by: Jasen Sumalapao
ALIASES:

Backdoor:Win32/Briba.A (Microsoft), Backdoor.Briba (Symantec), Mal/Behav-116 (Sophos), Gen:Variant.Barys.984 (Fsecure), Trojan.Win32.Generic!BT (Sunbelt), W32/Briba.AA (Fortinet), Backdoor.Win32.Briba (Ikarus), Win32/Briba.AA trojan (NOD32)

 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

Infection Channel: Downloaded from the Internet, Dropped by other malware

This backdoor may be downloaded by other malware/grayware/spyware from remote sites. It arrives as a component bundled with malware/grayware packages. It may be dropped by other malware.

It is injected into all running processes to remain memory resident.

It executes commands from a remote malicious user, effectively compromising the affected system.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system. As of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 90,112 bytes
File Type: EXE, DLL
Memory Resident: Yes
Initial Samples Received Date: 15 Aug 2012
Payload: Connects to URLs/IPs, Terminates processes

Arrival Details

This backdoor may be downloaded by other malware/grayware/spyware from remote sites.

It arrives as a component bundled with malware/grayware packages.

It may be dropped by the following malware:

  • TROJ_MDROP.EVL

Installation

This backdoor drops the following component file(s):

  • %User Profile%\Application Data\taskman.dll - detected as BKDR_BRIBA.EVL

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It is injected into all running processes to remain memory resident.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
rundll32.exe = "%User Profile%\Application Data\taskman.dll, start"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Execute command shell
  • Get system information
  • Create/delete folders
  • Create/terminate process
  • Download and execute other malicious files

Download Routine

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

  • http://publicnews.{BLOCKED}o.com/logo.gif

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

As of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.326.07
FIRST VSAPI PATTERN DATE: 15 Aug 2012
VSAPI OPR PATTERN File: 9.327.00
VSAPI OPR PATTERN Date: 16 Aug 2012

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

Remove the malware/grayware file that dropped/downloaded BKDR_BRIBA.EVL

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • rundll32.exe = "%User Profile%\Application Data\taskman.dll, start"

Step 5

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