BKDR_YOBDAM.AF

February 04, 2013
 ALIASES:

Backdoor:Win32/Morix.B (Microsoft); Generic BackDoor!1tp (McAfee); Trojan.Gen.2 (Symantec); Backdoor.Win32.Yobdam.jyq (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse SHeur4.AFGK (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor 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:

847,872 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

04 Feb 2013

Arrival Details

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

  • %Program Files%\tPDrx\MTKti.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It creates the following folders:

  • %Program Files%\tPDrx

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MTKti.exe = "%Program Files%\tPDrx\MTKti.exe"

Other System Modifications

This backdoor deletes the following files:

  • %User Temp%\tst1.tmp
  • %User Temp%\tst2.tmp
  • %User Temp%\tst3.tmp
  • %User Temp%\tst4.tmp
  • %User Temp%\tst5.tmp

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\Options

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\Text

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\RTF

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\Word6

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\Write

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\IP

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\Recent File List

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Applets\
Wordpad\Settings

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\MTKti.doc
  • %User Temp%\ms4414.tmp

(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, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets
    • Wordpad
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • Options
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • Text
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • RTF
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • Word6
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • Write
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • IP
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • Recent File List
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Applets\Wordpad
    • Settings

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
    • MTKti.exe = "%Program Files%\tPDrx\MTKti.exe"

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.
  • %User Temp%\MTKti.doc
  • %User Temp%\ms4414.tmp

Step 6

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.
  • %Program Files%\tPDrx

Step 7

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

Step 8

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.

  • %User Temp%\tst1.tmp
  • %User Temp%\tst2.tmp
  • %User Temp%\tst3.tmp
  • %User Temp%\tst4.tmp
  • %User Temp%\tst5.tmp


Did this description help? Tell us how we did.