BKDR_ZEGOST.ECB

February 18, 2013
 Analysis by: Rhena Inocencio
 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:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware

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 may be dropped by other malware.

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

  TECHNICAL DETAILS

File Size:

196,608 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

15 Feb 2013

Payload:

Connects to URLs/IPs, Logs keystrokes, Drops files, Terminates processes

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.

It may be dropped by the following malware:

  • TROJ_DROPPER.ECB

Installation

This backdoor drops the following copies of itself into the affected system:

  • %Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}
ImagePath = "%System%\rundll32.exe "%Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.dll",ServiceBoot"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}
Type = "110"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\{random file name}

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Enum\Root\LEGACY_{random file name}

Backdoor Routine

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

  • Browse files
  • Manage files
  • Download and execute arbitrary files
  • Execute shell commands
  • Enumerate running processes
  • Terminate processes
  • Get drive information
  • Log Keystrokes
  • Logs the user off
  • Copy clipboard data

Other Details

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

  • {All User's Profile}\{random file name}.dat
  • %User Temp%\{random}_{random}.vbs - deleted after execution
  • %Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.ini - configuration file containing the location of BKDR_ZEGOST.ECB and TROJ_DROPPER.ECB

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

NOTES:

This backdoor connects to the following command-and-control (C&C) server to send and receive commands:

  • {BLOCKED}l.{BLOCKED}ews.com

  SOLUTION

Minimum Scan Engine:

9.300

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_ZEGOST.ECB

Step 3

Remove the malware/grayware file that dropped/downloaded BKDR_ZEGOST.ECB

Step 4

Restart in Safe Mode

[ Learn More ]

Step 5

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • {random file name}
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Enum\Root
    • LEGACY_{random file name}

Step 6

Search and delete the file detected as BKDR_ZEGOST.ECB

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 7

Search and delete these files

[ 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.
  • {All User's Profile}\{random file name}.dat
  • %Program Files%\Common Files\Microsoft Shared\MSInfo\{random file name}.ini

Step 8

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