BKDR_URSNIF.E

April 25, 2013
 Analysis by: Merianne Polintan
 ALIASES:

TrojanSpy:Win32/Ursnif(Microsoft),Mal/Generic-L(Sophos),Trojan.Win32.Generic!BT(Sunbelt),W32/Kryptik.SQL!tr(Fortinet),Trojan W32/Suspicious_Gen2.SKUCG(Norman)

 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:

  • 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.

It executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

125,440 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

23 Apr 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 files:

  • %User Temp%\2FAD_APPCOMPAT.TXT

(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 drops the following copies of itself into the affected system:

  • %User Profile%\nah_lovs.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.)

It executes then deletes itself afterward.

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
nah_Shell = "%User Profile%\nah_lovs.exe"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
"nah_opt_reserv" = "213.239.217.59"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
nah_opt_server1 = "213.155.28.104"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion
nah_opt_server = "213.239.217.59"

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

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

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

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

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

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

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

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.28.104/system/prinimalka.py/options?user_id=8132048881&version_id=001902&crc=34661b26&uptime=00:00:15:54&port=5536&ip=
  • http://{BLOCKED}.{BLOCKED}.28.104/system/prinimalka.py/command?user_id=8132048881&version_id=001902&crc=00000000

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.874.03

FIRST VSAPI PATTERN DATE:

23 Apr 2013

VSAPI OPR PATTERN File:

9.875.00

VSAPI OPR PATTERN Date:

24 Apr 2013

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

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.
  • %User Temp%\2FAD_APPCOMPAT.TXT

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
    • nah_Shell = "%User Profile%\nah_lovs.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • "nah_opt_reserv" = "213.239.217.59"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_server1 = "213.155.28.104"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_server = "213.239.217.59"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_forms = "/system/prinimalka.py/forms"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_options = "/system/prinimalka.py/options"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_command = "system/prinimalka.py/command"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_file = "/system/prinimalka.py/cookies"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_ss = "/cgi-bin/trash.py"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_pstorage = "/cgi-bin/trash.py"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
    • nah_opt_certs = "/cgi-bin/trash.py"

Step 5

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