Analysis by: Anthony Joe Melgarejo


Backdoor:Win32/Wkysol.G (Microsoft), Backdoor.Sykipot!gen3 (Symantec), BackDoor-FDE.b (McAfee)


Windows 2000, Windows XP, Windows Server 2003


  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes


This backdoor may be dropped by other malware.

It does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It takes advantage of certain vulnerabilities.


File Size: Varies
File Type: DLL, EXE
Memory Resident: Yes
Initial Samples Received Date: 16 Nov 2012
Payload: Connects to URLs/IPs, Compromises system security

Arrival Details

This backdoor may be dropped by the following malware:



This backdoor drops the following component file(s):

  • %User Profile%\Local Settings\{malware file name 1}.dll - also detected as BKDR_WKYSOL.SM
  • %User Profile%\Local Settings\setm.ini
  • %User Temp%\tpdefense.dat

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

It is injected into the following processes running in memory:


Autostart Technique

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

start = "{folder where malware is located}\{malware file name 2}.exe -installkys"


This backdoor does not have any propagation routine.

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download and Upload arbitrary files
  • Command Shell
  • Create/Terminate Process
  • Create,Open and Delete files
  • Reboot the computer

It connects to the following websites to send and receive information:

  • http://www.{BLOCKED}

As of this writing, the said sites are inaccessible.

Other Details

This backdoor takes advantage of the following vulnerabilities:


This backdoor gets its settings from the configuration file %User Profile%\Local Settings\setm.ini. This configuration file contains the following:

  • Sleep time of the malware
  • The URL it connects to
  • File names of the component files
  • Bot ID

It connects to the following remote site to download a possible configuration or component file that contains its intended routines and send back information such as host name and IP address:

  • http://{malicious site}/kys_allow_get.asp?name=getkys.jpg&hostname={hostname}-{IP Address}

This backdoor is also capable of deleting the registry entries it adds when the parameter -removekys is passed on to it by its component file.

It does not have rootkit capabilities.

Note that {malware file name 1} can be any of the following:

  • date.dll
  • update.dll

And {malware file name 2} can be any of the following:

  • EBWin.exe
  • update.exe


Minimum Scan Engine: 9.300
VSAPI OPR PATTERN File: 9.531.00
VSAPI OPR PATTERN Date: 17 Nov 2012

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 BKDR_WKYSOL.SM

Step 3

Scan your computer with your Trend Micro product and note files detected as BKDR_WKYSOL.SM

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • start = "{folder where malware is located}\{malware file name 2}.exe -installkys"

Step 6

Search and delete these files

[ 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.
  • %User Profile%\Local Settings\setm.ini
  • %User Temp%\tpdefense.dat

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_WKYSOL.SM. 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.

Step 8

Download and apply these security patches Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.

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