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Malware type: Trojan
Destructive: No
Platform: Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
Encrypted: Yes
In the wild: Yes


Infection Channel: Dropped by other malware

This malware is the final payload of a targeted attack campaign leveraging the April 2013 Boston Marathon Bombing. It downloads malicious files onto the systems it infects. Affected users may find their systems infected with other malicious files that this malware downloads.

To get a one-glance comprehensive view of the behavior of this Trojan, refer to the Threat Diagram shown below.

This Trojan may be dropped by other malware.

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

Technical Details

File size: 56,320 bytes
File type: EXE
Memory resident: Yes
Initial samples received date: 19 Apr 2013
Payload: Connects to URLs/IPs, Compromises system security, Downloads files, Drops files

Arrival Details

This Trojan may be dropped by the following malware:



This Trojan drops the following copies of itself into the affected system and executes them:

  • %System%\ymsgr_tray.exe

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

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

  • {malware path}\profile.dat - blob file containing malware routines

It adds the following processes:

  • iexplore.exe

It injects itself into the following processes as part of its memory residency routine:

  • iexplore.exe

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

Yahoo! = ""%System%\ymsgr_tray.exe" -local"

Other Details

This Trojan attempts to access the following websites to download files, which are possibly malicious:

  • {BLOCKED}point.{BLOCKED}

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


The malware needs the following command line parameters in order to perform its intended routine:

  • -{any string}cal


Minimum scan engine: 9.300
First VSAPI Pattern File: 9.866.06
First VSAPI Pattern Release Date: 20 Apr 2013
VSAPI OPR Pattern Version: 9.867.00
VSAPI OPR Pattern Release Date: 20 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

Remove the malware/grayware file that dropped/downloaded TROJ_NAIKON.A


Step 3

Scan your computer with your Trend Micro product and note files detected as TROJ_NAIKON.A

Step 4

Restart in Safe Mode

[ Learn more ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Yahoo! = ""%System%\ymsgr_tray.exe" -local"

Step 6

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.
  • {malware path}\profile.dat

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_NAIKON.A. 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: Abraham Latimer Camba

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