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BKDR_XTRAT.JT
Aliases: W32/VBKrypt.NQYR!tr (Fortinet), Virus.Win32.CryptExe (Ikarus), probably a variant of Win32/Agent.KPYNHWZ trojan (NOD32)
Malware type: Backdoor
Destructive: No
Platform: Windows 2000, Windows XP, Windows Server 2003
Encrypted: Yes
In the wild: Yes

Overview


Infection Channel: Downloaded from the Internet, Dropped by other malware

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.

However, as of this writing, the said sites are inaccessible.

It steals system information. It logs a user's keystrokes to steal information.

Technical Details


File size: 734,480 bytes
File type: EXE
Memory resident: Yes
Initial samples received date: 13 Nov 2012
Payload: Compromises system security, Steals information

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 and executes them:

  • %User Temp%\ie4uinit.exe

(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.)

It drops the following file(s)/component(s):

  • %Application Data%\Microsoft\Crypto\RSA\S-1-5-21-1614895754-436374069-682003330-1003\c0528c2346cb928a9052304ef3ab8fd4_411f3a52-26ed-4872-9a07-8c966acba234

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

Autostart Technique

This backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
ie4uinit.exe = %User Temp%\ie4uinit.exe -h"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Software\XtremeRAT
Mutex = "--((Mutex))--"

HKEY_CURRENT_USER\Software\--((Mutex))--
ServerStarted = "{Date and Time}"

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

HKEY_CLASSES_ROOT\rr1081767346z.ypa

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
rr1081767346z.ypa

Backdoor Routine

This backdoor opens the following port(s) where it listens for remote commands:

  • TCP port 8888

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}g.{BLOCKED}p.org:1500/1411.functions

However, as of this writing, the said sites are inaccessible.

Information Theft

This backdoor steals system information.

It logs a user's keystrokes to steal information.

Stolen Information

The stolen information is saved in the following file:

  • %Application Data%\Microsoft\Windows\--((Mutex))--.dat

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, XP, and Server 2003.)

Solution


Minimum scan engine: 9.200
First VSAPI Pattern File: 9.524.02
First VSAPI Pattern Release Date: 13 Nov 2012
VSAPI OPR Pattern Version: 9.525.00
VSAPI OPR Pattern Release Date: 14 Nov 2012

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Terminate a malware/grayware process

[ Learn more ]

*Note: If the detected process is not displayed in theWindows Task Manager, continue doing the next steps.

    • ie4uinit.exe

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\--((Mutex))--
    • ServerStarted
  • In HKEY_CURRENT_USER\Software\XtremeRAT
    • Mutex
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • ie4uinit.exe

Step 4

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
    • rr1081767346z.ypa
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes
    • rr1081767346z.ypa

Step 5

Search and delete this file

[ Learn more ]
There may be some component 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.
  • %Application Data%\Microsoft\Crypto\RSA\S-1-5-21-1614895754-436374069-682003330-1003\c0528c2346cb928a9052304ef3ab8fd4_411f3a52-26ed-4872-9a07-8c966acba234
  • %Application Data%\Microsoft\Windows\--((Mutex))--.dat

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_XTRAT.JT. 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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Analysis By: Nikko Tamana

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