Analysis by: Pearl Charlaine Espejo
ALIASES:

TrojanDownloader:Win32/Tonnejoom.A (Microsoft); Backdoor.Bot (Malwarebytes); TR/AD.Bunitu.Y.41 (Avira); Trojan.Win32.Swizzor.1!O (CMC)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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.

  TECHNICAL DETAILS

File Size: 197,108 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 03 Sep 2015

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.

Autostart Technique

This Trojan drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\system.pif → copy of itself

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This Trojan modifies the following file(s):

  • {firefox path}\prefs.js

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
AutoConfigURL = "https://puretonnel.net/3desonnel.js"

Dropping Routine

This Trojan drops the following files:

  • %All Users Profile%\cert{value}.der

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Download Routine

This Trojan saves the files it downloads using the following names:

  • %All Users Profile%\Microsoft-KB{random}.exe
    or
  • %All Users Profile%\WindowsXP-KB{random}.exe

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://www.{BLOCKED}zerhof-wetzikon.ch/images/rtucrtmirumctrutbitueriumxe/ivotyimoyctorieotcmir.exe
  • http://{BLOCKED}a.{BLOCKED}i.at/vs28/schule/administrator/components/com_phocagallery/c.exe
  • http://www.{BLOCKED}unter.com/counter.php?vtrtvrvtrtvertvr
  • http://www.{BLOCKED}unter.com/counter.php?tcrcrcerererwbvbbrtdf

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 11.898.05
FIRST VSAPI PATTERN DATE: 04 Sep 2015
VSAPI OPR PATTERN File: 11.899.00
VSAPI OPR PATTERN Date: 05 Sep 2015

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • AutoConfigURL = "https://puretonnel.net/3desonnel.js"

Step 4

Search and delete these files

[ 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.
  • %All Users Profile%\Microsoft-KB{random}.exe
  • %All Users Profile%\WindowsXP-KB{random}.exe
  • %All Users Profile%\cert{value}.der

Step 5

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.  

  • {firefox path}\prefs.js

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_WERDLOD.V. 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.


Did this description help? Tell us how we did.