Analysis by: Christopher Daniel So
ALIASES:

TrojanDownloader:Win32/Tracur.AG (Microsoft)

 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

This Trojan may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size: 606.208 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 18 Oct 2011

Arrival Details

This Trojan may be dropped by other malware.

It may be unknowingly downloaded by a user while visiting malicious websites.

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\{random file name}.tmp - detected by Trend Micro as TROJ_ADCLICK.DV
  • %Application Data%\{random folder}\{random folder}Update\{random folder}updt32.dll - detected by Trend Micro as TROJ_ADCLICK.DV
  • %Application Data%\{random string 1}{random string2}.dll - detected by Trend Micro as TROJ_ADCLICK.DV

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003.. %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

NOTES:

It executes the dropped files by executing the following commands:

  • rundll32.exe "%User Temp%\{random file name}.tmp" DllRegisterServer
  • rundll32.exe "%Application Data%\{random folder}\{random folder}Update\{random folder}updt32",DllUnregisterServer
  • rundll32.exe "%Application Data%\{random folder}\{random folder}Update\{random folder}updt32",DllRegisterServer
  • rundll32.exe "%Application Data%\{random string 1}{random string2}.dll",DllRegisterServer

Random string 1 could be any of the following:

  • Explorer
  • Hardware
  • Internet
  • Network
  • Security
  • Service
  • Shell
  • System
  • TCPIP
  • Tray

Random string 2 could be any of the following:

  • Admin
  • Codec
  • PTR
  • SYS
  • Sys32
  • User
  • Win32
  • WMP
  • WOW64
  • x86_x64

This Trojan accesses the following websites to download files:

  • http://www.adobe.com/go/full_flashplayer_win_msi
  • http://fpdownload.macromedia.com/get/flashplayer/current/licensing/win/install_flash_player_10_active_x.msi

It executes the downloaded files.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.504.07
FIRST VSAPI PATTERN DATE: 17 Oct 2011

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_DROPPER.QNB

    • TROJ_ADCLICK.DV

Step 3

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPER.QNB. 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:
RECOMMENDATIONS:

Enable firewall to protect against web threats.

Block malware related websites.

When a computer is compromised, isolate it immediately from the network.

Always keep pattern files/engine up-to-date.

Avoid visiting un-trusted sites that may redirect or download malware into the system.

Configure your email server to block or remove email that contains file

attachments such as .vbs, .bat, .exe, .pif and .scr files.

Avoid opening e-mail attachments unless expected.

Avoid downloading crack applications.

Be aware of social engineering attacks to be safe.

Back up data regularly.


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