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VBS_OBFUCA.FA

October 09, 2012
 Analysis by: Rhena Inocencio
 ALIASES:

Trojan.VBS.Agent.nt (Kaspersky)

 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

Infection Channel:

Dropped by other malware, Downloaded from the Internet


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 may be hosted on a website and run when a user accesses the said website.

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

11,587 bytes

File Type:

VBS

Initial Samples Received Date:

06 Jul 2012

Payload:

Downloads files

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.

It may be hosted on a website and run when a user accesses the said website.

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
PortGate

Download Routine

This Trojan saves the files it downloads using the following names:

  • {Malware Path}\{random file name}.wsf

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{random domain}Cache/hc/Current.htm

However, as of this writing, the said sites are inaccessible.

NOTES:

This Trojan requires registry entries in the following registry key to perform its intended routine:

HKEY_CURRENT_USER\Software\Microsoft\PortGate

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.242.06

FIRST VSAPI PATTERN DATE:

08 Jul 2012

VSAPI OPR PATTERN File:

9.243.00

VSAPI OPR PATTERN Date:

08 Jul 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

Scan your computer with your Trend Micro product and note files detected as VBS_OBFUCA.FA

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_CURRENT_USER\Software\Microsoft
    • PortGate

Step 4

Search and delete this file

[ Learn More ]

There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.
  • {Malware Path}\{random file name}.wsf

Step 5

Scan your computer with your Trend Micro product to delete files detected as VBS_OBFUCA.FA. 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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