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TROJ_DROPPER.YXK

September 07, 2013
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

399,048 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

07 Sep 2013

Arrival Details

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\TZNLVCNDG

HKEY_LOCAL_MACHINE\Software\TZNLVCNDG

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run

It adds the following registry entries:

HKEY_CURRENT_USER\Software\TZNLVCNDG
Cyryaed = "{random values}"

HKEY_LOCAL_MACHINE\SOFTWARE\TZNLVCNDG
Cyryaed = "{random values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
Rvuobygkmb = "%System%\nmmkcertt.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
6 = "{random values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
6 = "{random values}"

Dropping Routine

This Trojan drops the following files:

  • %System%\nmmkcertt.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}175.164/section/view/index.jsp

It deletes itself after execution.

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

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
    • TZNLVCNDG
  • In HKEY_LOCAL_MACHINE\Software
    • TZNLVCNDG
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • Run

Step 3

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\TZNLVCNDG
    • Cyryaed = "{random values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\TZNLVCNDG
    • Cyryaed = "{random values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • Rvuobygkmb = "%System%\nmmkcertt.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings
    • 6 = "{random values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • 6 = "{random values}"

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.
  • %System%\nmmkcertt.exe

Step 5

Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPER.YXK. 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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