Analysis by: Christopher Daniel So

ALIASES:

Worm:ALisp/Blemfox.A (Microsoft), Worm.Acad.Medre.a (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel: Dropped by other malware, Downloaded from the Internet

This malware steals designs and drawings from affected users. It also steals the .PST files on the infected system, which cybercriminals can use for other malicious activities.

To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.

This malware checks the version of AutoCAD installed and modifies certain files depending on the version installed.

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.

  TECHNICAL DETAILS

File Size: Varies
File Type: LSP
Initial Samples Received Date: 25 Jun 2012

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 copies of itself into the affected system:

  • %System%\Acad.fas
  • %System%\Ȥζ»úеÖÆͼ\acad.fas
  • %Windows%\Acad.fas
  • {AutoCAD support search path}\acad.fas
  • {AutoCAD support search path}\cad.fas
  • {current drawing path}\cad.fas
  • {current drawing path}\Acad.fas

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It creates the following folders:

  • %System%\Ȥζ»úеÖÆͼ

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Other System Modifications

This worm adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\Windows Error Reporting
FILE-H = "T"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\Windows Error Reporting
Time = "{random number}"

NOTES:

This worm checks the version of AutoCAD installed and modifies one of the following files depending on the version installed:

  • acad2000.lsp
  • acad2002.lsp
  • acad2004.lsp
  • acad2005.lsp
  • acad2006.lsp
  • acad2007.lsp
  • acad2008.lsp
  • acad2009.lsp
  • acad2010.lsp
  • acad2011.lsp
  • acad2012.lsp
  • acad2013.lsp
  • acad2014.lsp
  • acad2015.lsp

It inserts a single line to one of the files above to automatically load the malware copy named CAD.FAS.

It searches for .PST files by enumerating the registry entries in the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Catalog

HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Catalog

HKEY_CURRENT_USER\Software\Microsoft\Office\13.0\Outlook\Catalog

It sends an email to {BLOCKED}qyg@163.com with attached .PST files. It also sends another email with an attachment containing the currently opened drawing file to the same email address.

It drops the file %System%\Ȥζ»úеÖÆͼ\Ȥζ»úеÖÆͼ.dxf, which contains information about the current drawing. It then creates an encrypted RAR archive named %System%\Ȥζ»úеÖÆͼ.rar with the password 1. It adds a copy of itself and %System%\Ȥζ»úеÖÆͼ\Ȥζ»úеÖÆͼ.dxf into the archive.

  SOLUTION

Minimum Scan Engine: 9.200
VSAPI OPR PATTERN File: 9.217.00
VSAPI OPR PATTERN Date: 26 Jun 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

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\Windows Error Reporting
    • FILE-H = "T"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\Windows Error Reporting
    • Time = "{random number}"

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.
  • %System%\Ȥζ»úеÖÆͼ

Step 4

Scan your computer with your Trend Micro product to delete files detected as ACM_MEDRE.SM2. 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.

NOTES:

Restoring Modified AutoCAD LSP File

  1. Open the file acad20??.lsp in Notepad.
  2. Search for the following line in the file:
    (if (findfile "cad.fas")(load "cad.fas"))
  3. Delete the aforementioned line.
  4. Save and close Notepad.


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