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Aliases: Troj/Blocker-Y (Sophos) ,Trojan horse Crypt2.CKYQ (AVG) ,W32/Blocker.DPCS!tr (Fortinet) ,Trojan.Win32.Foidan (Ikarus) ,Trojan-Ransom.Win32.Blocker.dpcs (Kaspersky) ,Trojan:Win32/Foidan.B (Microsoft) ,RDN/Ransom!eb (McAfee) ,a variant of Win32/Kryptik.BUHD trojan (Eset) ,Trj/dtcontx.J (Panda) ,Trojan.Win32.Generic!BT (Sunbelt)
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: Downloaded from the Internet

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

It gathers certain information on the affected computer.

Technical Details

File size: 104,960 bytes
File type: EXE
Memory resident: Yes
Initial samples received date: 21 Feb 2014
Payload: Collects system information

Arrival Details

This Trojan may be downloaded by the following malware/grayware from remote sites:



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

  • %Application Data%\fnmod_32.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • SYS_A7F20C8D{4 digit number}
  • SYS_B82C5620{4 digit number}

It is injected into the following processes running in memory:

  • dwm.exe
  • taskhost.exe
  • taskeng.exe
  • wscntfy.exe
  • ctfmon.exe
  • rdpclip.exe
  • explorer.exe
  • iexplore.exe

Autostart Technique

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

FNModuleUpdater = "%Application Data%\fnmod_32.exe"

Information Theft

This Trojan gathers the following information on the affected computer:

  • OS Version
  • System Information (32-bit / 64-bit)


It hooks the following API to disable X-Frame-Options security feature to enable clickjacking routines:

  • InternetReadFile
  • HttpQueryInfoA


Minimum scan engine: 9.700
First VSAPI Pattern File: 10.620.01
First VSAPI Pattern Release Date: 21 Feb 2014
VSAPI OPR Pattern Version: 10.621.00
VSAPI OPR Pattern Release Date: 22 Feb 2014

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_FOIDAN.AX

Step 3

Restart in Safe Mode

[ Learn more ]

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
    • FNModuleUpdater = "%Application Data%\fnmod_32.exe"

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_FOIDAN.AX. 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: Mark Joseph Manahan

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