BKDR_ZAPCHAST.BL

September 05, 2013
 Analysis by: Rika Joi Gregorio
 ALIASES:

Trojan-Spy.Win32.Zapchast.t(Kaspersky), Trojan:Win32/Sisproc(Microsoft)

 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:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

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

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

22,016 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Sep 2013

Payload:

Compromises system security

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 copies of itself into the affected system and executes them:

  • %System%\sve.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • PpPPpPPpPPpPPpPPpP

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Adobe_RLX = "%System%\sve.exe 1 2"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random}
StubPath = "%System%\sve.exe 1 2"

Backdoor Routine

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

  • Download File
  • Download and Execute File
  • Update Itself
  • Perform remote shell command

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • {BLOCKED}g.{BLOCKED}L.com
  • {BLOCKED}t.{BLOCKED}b.com

Other Details

This backdoor deletes itself after execution.

NOTES:

It searches for AV-related files:

  • ESET
  • Avira
  • Trend Micro
  • AVAST
  • McAfee
  • Panda Security
  • AVG
  • Kaspersky
  • Symantec
  • Norton

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.258.01

FIRST VSAPI PATTERN DATE:

04 Sep 2013

VSAPI OPR PATTERN File:

10.259.00

VSAPI OPR PATTERN Date:

05 Sep 2013

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

Restart in Safe Mode

[ Learn More ]

Step 3

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\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {random}

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Adobe_RLX = "%System%\sve.exe 1 2"

Step 5

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