BKDR_URSNIF.F

 Analysis by: Maydalene Edsel Salvador

 ALIASES:

TrojanSpy:Win32/Ursnif.gen!F (Microsoft), PWS-Zbot.gen.ana (NAI), Mal/EncPk-AGK (Sophos), Mal/EncPk-AGK (Sunbelt), Win32/Cryptor (AVG), Trojan.Generic.KDV.691938 (BitDefender), W32/Kryptik.AJTM!tr (Fortinet), Trj/Pacrypt.C (Panda), Trojan.Win32.Matsnu (Ikarus)

 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:
 SYSTEM IMPACT RATING:

  • 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:

145,920 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

01 Sep 2012

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:

  • %User Profile%\gov{4_RANDOM_CHAR}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

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
govShell = "%User Profile%\gov{4_RANDOM_CHAR}.exe"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govid = "2533639800"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govoptions =

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_server1 = "93.115.241.114"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_reserv = "93.115.241.114"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_forms = "/system/prinimalka.py/forms"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_options = "/system/prinimalka.py/options"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_command = "/system/prinimalka.py/command"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_file = "/system/prinimalka.py/cookies"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_ss = "/cgi-bin/trash.py"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_pstorage = "/cgi-bin/trash.py"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_certs = "/cgi-bin/trash.py"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_idproject = "081001"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
govopt_pauseopt = "3200"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.241.114/system/prinimalka.py/forms
  • http://{BLOCKED}.{BLOCKED}.241.114/system/prinimalka.py/options
  • http://{BLOCKED}.{BLOCKED}.241.114/system/prinimalka.py/command
  • http://{BLOCKED}.{BLOCKED}.241.114/system/prinimalka.py/cookies

  SOLUTION

Minimum Scan Engine:

9.300

VSAPI OPR PATTERN File:

9.874.04

VSAPI OPR PATTERN Date:

08 Aug 2012

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

Scan your computer with your Trend Micro product and note files detected as BKDR_URSNIF.F

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Search and delete this file

[ 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.  
  • gov{4_RANDOM_CHAR}.exe

Step 5

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
    • govShell = "%User Profile%\gov{4_RANDOM_CHAR}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govid = "2533639800"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govoptions
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_server1 = "93.115.241.114"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_reserv = "93.115.241.114"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_forms = "/system/prinimalka.py/forms"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_options = "/system/prinimalka.py/options"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_command = "/system/prinimalka.py/command"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_file = "/system/prinimalka.py/cookies"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_ss = "/cgi-bin/trash.py"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_pstorage = "/cgi-bin/trash.py"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_certs = "/cgi-bin/trash.py"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_idproject = "081001"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • govopt_pauseopt = "3200"

Step 6

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