Analysis by: Christopher Daniel So
ALIASES:

Trojan:Win32/Alyak.C (Microsoft), Trojan.Gen (Symantec)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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 deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 208,951 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 06 Oct 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.

Installation

This Trojan drops the following copies of itself into the affected system:

  • %System%\V3Medic.exe

(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.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random CLSID}
stubpath = "%SystemRoot%\system32\V3Medic.exe"

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Ole
Version = "{random number}"

Download Routine

This Trojan connects to the following website(s) to download and execute a malicious file:

  • http://www.{BLOCKED}nomy.com/xml/20110517/t2.gif

Trend Micro detects the dowloaded file as:

  • TROJ_SPYDROP.AD

Other Details

This Trojan connects to the following URL(s) to check for an Internet connection:

  • http://blog.sina.com.cn/s/blog_af5f75a301015gge.html

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 9.442.05
FIRST VSAPI PATTERN DATE: 05 Oct 2012
VSAPI OPR PATTERN File: 9.443.00
VSAPI OPR PATTERN Date: 06 Oct 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

Remove malware files dropped/downloaded by TROJ_ALYAK.AD

    • TROJ_SPYDROP.AD

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{random CLSID}
    • stubpath = "%SystemRoot%\system32\V3Medic.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Ole
    • Version = "{random number}"

Step 4

Scan your computer with your Trend Micro product to delete files detected as TROJ_ALYAK.AD. 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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