TROJ_TRACUR.SMA

 Analysis by: Christopher Daniel So

 ALIASES:

TrojanDownloader:Win32/Tracur.R (Microsoft)

 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW


This Trojan may be downloaded by other malware/grayware/spyware from remote sites. It may be dropped by other malware. It may be unknowingly downloaded by a user while visiting malicious websites.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Apr 2011

Payload:

Downloads files

Arrival Details

This Trojan may be downloaded by other malware/grayware/spyware from remote sites.

It may be dropped by other malware.

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

Installation

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

  • %Windows%\{random characters}wow.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.)

It drops the following non-malicious file:

  • %System%\A887E64515035F9F82BAF1D4BC896D65\unrar.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It creates the following folders:

  • %System%\A887E64515035F9F82BAF1D4BC896D65
  • %System%\A887E64515035F9F82BAF1D4BC896D65\b
  • %System%\A887E64515035F9F82BAF1D4BC896D65\h

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random characters}wow.exe = "%Windows%\{random characters}wow.exe"

Other System Modifications

This Trojan creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%Windows%\{random characters}wow.exe = "%Windows%\{random characters}wow.exe:*:Enabled:Windows Update Service"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Windows%\{random characters}wow.exe = "%Windows%\{random characters}wow.exe:*:Enabled:Windows Update Service"

Download Routine

This Trojan downloads an updated copy of itself from the following website(s):

  • http://{BLOCKED}230.12/bin_v85.rar

It connects to the following URL(s) to download its configuration file:

  • http://{BLOCKED}.1.174/update/{random characters}
  • http://{BLOCKED}.53.210/update/{random characters}
  • http://{BLOCKED}.153.48/update/{random characters}

It saves the files it downloads using the following names:

  • %System%\A887E64515035F9F82BAF1D4BC896D65\{random number}.tmp

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

NOTES:

The downloaded configuration file contains the URLs containing the update. The URLs are saved in the file %System%\A887E64515035F9F82BAF1D4BC896D65\ntuser.dat. However, the configuration file is not saved in the computer.

The downloaded update is a compressed .RAR archive. It uses the dropped file %System%\A887E64515035F9F82BAF1D4BC896D65\unrar.exe to extract the compressed updated copy of the malware. It then executes the update with the command-line parameters -upd -fd%Windows%\{random characters}wow.exe. The command-line parameter -fd causes the newer version of the malware to delete the older version of the malware. Trend Micro detects the downloaded update as TROJ_TRACUR.SMB.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.944.11

FIRST VSAPI PATTERN DATE:

02 Apr 2011

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

Remove the malware/grayware file dropped/downloaded by TROJ_TRACUR.SMA

    TROJ_TRACUR.SMB

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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\Windows\CurrentVersion\Run
    • {random characters}wow.exe=%Windows%\{random characters}wow.exe
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %Windows%\{random characters}wow.exe=%Windows%\{random characters}wow.exe:*:Enabled:Windows Update Service
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Windows%\{random characters}wow.exe=%Windows%\{random characters}wow.exe:*:Enabled:Windows Update Service

Step 5

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%\A887E64515035F9F82BAF1D4BC896D65

Step 6

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