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WORM_DELF.RSN

October 16, 2013
 Analysis by: Jimelle Monteser
 ALIASES:

PWS:Win32/Sacanph.A (Microsoft); Generic.dx!9ABEE85DD07A (McAfee); Backdoor.Trojan (Symantec); Trojan.Win32.Delf.cfmj (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse PSW.Generic9.BTIW (AVG)

 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: Trojan

  • Destructiveness: No

  • Encrypted:

  • 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

768,512 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Oct 2013

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 copies of itself into the affected system:

  • %Application Data%\wmps.exe - for Windows XP
  • %AppDataLocal%\wmps.exe - for Windows 7

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.. %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Media service = "%Application Data%\wmps.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Media service = "%AppDataLocal%\wmps.exe"

Propagation

This Trojan drops the following copy(ies) of itself in all removable drives:

  • {Removable Drive Letter}:\New folder(1).exe

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}o.{BLOCKED}s.org

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.342.01

FIRST VSAPI PATTERN DATE:

15 Oct 2013

VSAPI OPR PATTERN File:

10.343.00

VSAPI OPR PATTERN Date:

16 Oct 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 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Media service = "%Application Data%\wmps.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Windows Media service = "%AppDataLocal%\wmps.exe"

Step 4

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