BKDR_WKYSOL.ED

 Analysis by: Jaime Benigno Reyes

 ALIASES:

Backdoor:Win32/Wkysol.E (Microsoft)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware


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.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

28 Jan 2013

Payload:

Connects to URLs/IPs, Compromises system security, Downloads files

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_MDROPPR.DCD

Installation

This backdoor drops the following component file(s):

  • %AppDataLocal%\pla.dll (Windows Vista and 7 only) - also detected as BKDR_WKYSOL.ED
  • %AppDataLocal%\setm.ini (Windows Vista and 7 only)
  • %User Profile%\Local Settings\pla.dll (versions other than Windows Vista and 7) - also detected as BKDR_WKYSOL.ED
  • %User Profile%\Local Settings\setm.ini (versions other than Windows Vista and 7)
  • %User Temp%\pfilede.dat

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

  • IEXPLORE.EXE

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
start = "{malware location}\{malware filename}.exe -startup"

Propagation

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
  • Perform command shell commands
  • Create/terminate process
  • Create, open, and delete files
  • Reboot the computer

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

  • http://{BLOCKED}7s.{BLOCKED}.net

NOTES:

This backdoor gets its settings from the configuration file setm.ini. This configuration file contains the following:

  • Sleep time of the malware
  • 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://{BLOCKED}7s.{BLOCKED}p.net/kys_allow_get.asp?name=getkys.jpg&hostname={hostname}-{IP Address}{Bot ID}
  • http://{BLOCKED}s.{BLOCKED}p.net/kys_allow_put.asp?type=put.jpg&hostname={hostname}-{IP Address}{Bot ID}

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.

It does not exploit any vulnerability.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

9.688.04

FIRST VSAPI PATTERN DATE:

29 Jan 2013

VSAPI OPR PATTERN File:

9.689.00

VSAPI OPR PATTERN Date:

30 Jan 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 BKDR_WKYSOL.ED

Step 3

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

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 = "{malware location}\{malware filename}.exe -startup"

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.
  • %AppDataLocal%\setm.ini (Windows Vista and 7 only)
  • %User Profile%\Local Settings\setm.ini (versions other than Windows Vista and 7)
  • %User Temp%\pfilede.dat

Step 7

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