Analysis by: Rika Joi Gregorio
ALIASES:

Trojan-Ransom.Win32.Foreign.rfg(Kaspersky), Win32/Injector.XDT trojan(Eset), Troj/Agent-YAO(Sophos)

 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:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm 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 then deletes itself afterward.

  TECHNICAL DETAILS

File Size: 177,664 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 29 Jan 2013

Arrival Details

This worm 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 worm drops the following files:

  • {Drive Letter}:\{folder name}.lnk - if the removable drive contains folders
  • {Drive Letter}:\RECYCLED\Desktop.ini

It executes then deletes itself afterward.

Propagation

This worm creates the following folders in all removable drives:

  • {Drive Letter}:\RECYCLED

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

  • {Drive Letter}:\RECYCLED\d1ff3a37.exe

Other Details

This worm connects to the following possibly malicious URL:

  • http://www.{BLOCKED}earch.net
  • http://{BLOCKED}.{BLOCKED}ia.com

NOTES:

It drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the folders located on the said drives for their file names. It then sets the attributes of the original folders to Hidden to trick the user into clicking the .LNK files.

  SOLUTION

Minimum Scan Engine: 9.300
FIRST VSAPI PATTERN FILE: 9.698.02
FIRST VSAPI PATTERN DATE: 31 Jan 2013
VSAPI OPR PATTERN File: 9.699.00
VSAPI OPR PATTERN Date: 02 Feb 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

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.
  • {Drive Letter}:\RECYCLED

Step 4

Search and delete this file

[ Learn More ]
There may be some 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.
  • {Drive Letter}:\{folder name}.lnk

Step 5

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