Analysis by: Karl Dominguez
 Modified by: jasperm
 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 malware arrives with other component files in a self-extracting archive downloaded unknowingly by a user from links in spammed messagels.

It uses the non-malicious files CSSRS.EXE and SYSTEM.EXE to connect to URLs using a random port. A remote malicious user will then be able to execute arbitrary commands in the affected system.

This backdoor arrives as a component bundled with malware/grayware packages. It may arrive using one or multiple arrival methods.

  TECHNICAL DETAILS

Ports: Random
File Size: 1,607 bytes
File Type: VBS
Memory Resident: Yes
Initial Samples Received Date: 08 Feb 2011

Arrival Details

This backdoor arrives as a component bundled with malware/grayware packages.

It arrives via the following means:

  • Dropped along with the following component files:
    • C:\Win.Msi\DiskDoctor.lnk - detected by Trend Micro as LNK_PENEPE.D
    • C:\Win.Msi\cssrs.exe - non-malicious file; open source proxy server from 3proxy.ru
    • C:\Win.Msi\System.exe - non-malicious file; open source command-line connection utility from PuTTY
  • Usually arrives with other component files in a self-extracting archive downloaded unknowingly by a user from links in spam messages

Other Details

This backdoor does the following:

  • Arrives with other component files in a self-extracting archive downloaded unknowingly by a user from links in spammed messages.
  • It also copies the shortcut file C:\Win.Msi\DiskDoctor.lnk into the %Startup% folder for its auto-start technique.


The said .LNK file is detected by Trend Micro as LNK_PENEPE.D Using the non-malicious files cssrs.exe and System.exe, the malware connects to the following URL using a random port. A remote malicious user will then be able to execute arbitrary commands in the affected system:
  • {BLOCKED}ga.zapto.org
  • {BLOCKED}a.zapto.org
  • {BLOCKED}ca.ath.cx

  SOLUTION

Minimum Scan Engine: 8.900

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 VBS_PENEPE.C

Step 3

Terminate a malware/grayware process

[ Learn More ]

*Note: If the detected process is not displayed in theWindows Task Manager, continue doing the next steps.

    wscript.exe
    cssrs.exe
    System.exe

Step 4

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.  C:\Win.Msi

Step 5

Scan your computer with your Trend Micro product to delete files detected as VBS_PENEPE.C. 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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