Threat Encyclopedia

TROJ_AMBLER.KA

Publish date: October 09, 2012

ANALYSIS BY

Karl Dominguez


PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type:Trojan

  • Destructiveness:No

  • Encrypted: Yes

  • In the wild: Yes

OVERVIEW


This Trojan may be downloaded by other malware/grayware/spyware from remote sites. It may be unknowingly downloaded by a user while visiting malicious websites.

It deletes itself after execution.

TECHNICAL DETAILS

File Size:

62,976 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

29 Nov 2010

Arrival Details

This Trojan may be downloaded by other malware/grayware/spyware from remote sites.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This Trojan drops the following files:

  • %User Profile%\Application Data\lrarts47.dll or %User Profile%\Application Data\juuglpbd5.dll -TSPY_AMBLER.KA
  • %User Profile%\Application Data\Sun\ftk

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

It creates the following folders:

  • %User Profile%\Application Data\Sun

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

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
lpc = "rundll32.exe %User Profile%\Application Data\Sun\{lrarts47.dll or juuglpbd5.dll}, RegisterDll"

Other System Modifications

This Trojan deletes the following files:

  • %User Profile%\Application Data\Sun\rwbbr.txt
  • %User Profile%\Application Data\Sun\oietr.txt
  • %User Profile%\Application Data\Sun\cngrh.txt
  • %User Profile%\Application Data\Sun\vntw.txt
  • %User Profile%\Application Data\Sun\mogr.txt
  • %User Profile%\Application Data\Sun\cetw.txt
  • %User Profile%\Application Data\Sun\mxd1.txt

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

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Clock
D1 = "2d 2d 21 2d 2d"

HKEY_CURRENT_USER\Software\Microsoft\
Clock
D2 = "22 20 2E 23 23"

HKEY_CURRENT_USER\Software\Microsoft\
Clock
D3 = "2f 22 2f 2c"

HKEY_CURRENT_USER\Software\Microsoft\
Clock
pr = "66 7A 78 70 70 64 76 7A 79 7B 7E 38 77 7A 7B"

Other Details

This Trojan deletes itself after execution.

SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.714.09

FIRST VSAPI PATTERN DATE:

21 Dec 2010

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

Remove malware files dropped/downloaded by TROJ_AMBLER.KA

    TSPY_AMBLER.KA

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
    • Clock

Step 4

Search and delete these folders

[ 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.
 %User Profile%\Application Data\Sun

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
    • lpc = "rundll32.exe %User Profile%\Application Data\Sun\{lrarts47.dll or juuglpbd5.dll}, RegisterDll"

Step 6

Scan your computer with your Trend Micro product to delete files detected as TROJ_AMBLER.KA. 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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