Analysis by: Kathleen Notario

ALIASES:

Trojan.Win32.Zapchast.pbs (Kaspersky); W32/Zapchast.PBS!tr (Fortinet)

 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 may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size: 4,096 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 10 Aug 2011

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_PIDIEF.EED

Installation

This backdoor adds the following processes:

  • %Program Files%\Internet Explorer\iexplore.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

Backdoor Routine

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

  • download file
  • execute file
  • execute command shell (cmd.exe)
  • kill process

It connects to the following websites to send and receive information:

  • *.dyndns.org

NOTES:

It also connects to the mentioned URL to report system infection and send system information such as:

  • hostname
  • ip address
  • machine name
  • OS name
  • proxy server
  • system time
  • username

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.426.03
FIRST VSAPI PATTERN DATE: 10 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

Remove the malware/grayware file that dropped/downloaded BKDR_ZAPCHAST.QZ

     TROJ_PIDIEF.EED

Step 3

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