Analysis by: Christopher Daniel So
ALIASES:

Trojan:Win32/Killav.DR (Microsoft), W32.Pykspa!gen1 (Symantec), Backdoor-EJG (McAfee), Backdoor.Win32.Zepfod.aco (Kaspersky), Troj/Bckdr-RAJ (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size: 651,264 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 12 Mar 2012

Arrival Details

This Trojan 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 Trojan drops the following component file(s):

  • %User Temp%\{random file name}.dll - detected by Trend Micro as TROJ_KILLAV.SMRB

(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.)

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\{random file name}.exe - detected by Trend Micro as WORM_SKYTWI.A

(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.)

NOTES:

It terminates and uninstalls the following files related to anti-virus software using its malware component TROJ_KILLAV.SMRB if found running in the system:

  • ashserv.exe
  • avgcsrvx.exe
  • avgrsx.exe
  • avgtray.exe
  • avguard.exe
  • avp.exe
  • bdagent.exe
  • ccsvchst.exe
  • ekrn.exe
  • fsgk32st.exe
  • gdscan.exe
  • mcmscsvc.exe
  • PsCtrlS.exe
  • pshost.exe
  • vsserv.exe
  • zlclient.exe

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.832.05
FIRST VSAPI PATTERN DATE: 13 Mar 2012
VSAPI OPR PATTERN File: 8.833.00
VSAPI OPR PATTERN Date: 13 Mar 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 malware files dropped/downloaded by TROJ_KILLAV.ARB

    • TROJ_KILLAV.SMRB
    • WORM_SKYTWI.A

Step 3

Identify and terminate files detected as TROJ_KILLAV.ARB

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_KILLAV.ARB. 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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