Analysis by: Sabrina Lei Sioting
ALIASES:

Trojan-Dropper.Win32.Bunitu (Ikarus), Backdoor.Win32.Symmi.qjx (Kaspersky), TrojanDropper:Win32/Bunitu.C (Microsoft),

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • 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.

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size: 106,496 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 22 Apr 2014

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
pdafoir = "rundll32 "%AppDataLocal%\pdafoir.dll",pdafoir"

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CLASSES_ROOT\Snakes.Document
{default} = "Snakes Document"

HKEY_CLASSES_ROOT\Snakes.Document\shell\
open\command
{default} = "{malware path}\{malware name}.exe "%1""

HKEY_CLASSES_ROOT\Snakes.Document\shell\
print\command
{default} = "{malware path}\{malware name}.exe /p "%1""

HKEY_CLASSES_ROOT\Snakes.Document\shell\
printto\command
{default} = "{malware path}\{malware name}.exe /pt "%1" "%2" "%3" "%4""

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Snakes.Document
{default} = "Snakes Document"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Snakes.Document\DefaultIcon
{default} = "{malware path}\{malware name}.exe,0"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Snakes.Document\shell\open\
command
{default} = "{malware path}\{malware name}.exe "%1""

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Snakes.Document\shell\print\
command
{default} = "{malware path}\{malware name}.exe /p "%1""

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Snakes.Document\shell\printto\
command
{default} = "{malware path}\{malware name}.exe /pt "%1" "%2" "%3" "%4""

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\pdafoir
DllName = "%AppDataLocal%\pdafoir.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\pdafoir
Startup = "pdafoir"

It adds the following registry keys as part of its installation routine:

HKEY_CLASSES_ROOT\Snakes.Document

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
Snakes

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Snakes.Document

HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
Snakes

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\pdafoir

Dropping Routine

This Trojan drops the following files:

  • %AppDataLocal%\pdafoir.dll

(Note: %AppDataLocal% is the Local Application Data folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local on Windows Vista and 7.)

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.742.06
FIRST VSAPI PATTERN DATE: 22 Apr 2014

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CLASSES_ROOT
    • Snakes.Document
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • Snakes.Document
  • In HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications
    • Snakes
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
    • pdafoir

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • pdafoir = "rundll32 "%AppDataLocal%\pdafoir.dll",pdafoir"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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. %AppDataLocal%\pdafoir.dll

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_BUNITU.SAV. 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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