Analysis by: Christopher Daniel So
ALIASES:

TrojanDownloader:Win32/Bredolab.AC (Microsoft); Backdoor.Win32.Bredolab.kaa (Kaspersky); Trojan-Downloader.Win32.Bredolab (GFI/Sunbelt); W32/Bredolab.KAA!tr.bdr (Fortinet); BDS/Bredolab.kaa (AntiVir)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This backdoor arrives as attachment to mass-mailed email messages. It may be dropped by other malware.

It connects to certain URLs. It may do this to remotely inform a malicious user of its installation. It may also do this to download possibly malicious files onto the computer, which puts the computer at a greater risk of infection by other threats. As of this writing, the said sites are inaccessible.

It opens a hidden Internet Explorer window.

  TECHNICAL DETAILS

File Size: 29,696 bytes
File Type: PE
File Compression: UPX
Memory Resident: Yes
Initial Samples Received Date: 17 Feb 2011
Payload: Downloads files

Arrival Details

This backdoor arrives as attachment to mass-mailed email messages.

It may be dropped by other malware.

Installation

This backdoor drops the following files:

  • %User Profile%\Application Data\mdjaw.dat

(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.)

Autostart Technique

This backdoor drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • algzcu32.exe - copy of itself

Download Routine

This backdoor connects to the following malicious URLs:

  • http://www.{BLOCKED}007.com/adm/controller.php?{random characters}

As of this writing, the said sites are inaccessible.

Other Details

This backdoor opens a hidden Internet Explorer window.

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 7.842.03
FIRST VSAPI PATTERN DATE: 17 Feb 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

Terminate a malware/grayware process

[ Learn More ]

*Note: If the detected process is not displayed in theWindows Task Manager, continue doing the next steps.

    • iexplore.exe

Step 3

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 Profile%\Application Data\mdjaw.dat

Step 4

Scan your computer with your Trend Micro product to delete files detected as BKDR_BREDOLAB.ZT. 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.