BKDR_CORKOW.VDH
Win32:Corkow-B [Trj] (Avast), Win32/Corkow.F (Eset), W32/Pincav.COMJ!tr (Fsecure), Trojan.Win32.Pincav (Ikarus), Trojan.Win32.Pincav.comj (Kaspersky), Trojan:Win32/Malagent (Microsoft),
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted: Yes
In the wild: Yes
OVERVIEW
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.
It retrieves specific information from the affected system.
It requires its main component to successfully perform its intended routine.
TECHNICAL DETAILS
Arrival Details
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This backdoor adds the following mutexes to ensure that only one of its copies runs at any one time:
- Global\{GUID}
It injects codes into the following process(es):
- java.exe
- javaw.exe
Other System Modifications
This backdoor adds the following registry entries as part of its installation routine:
HKEY_CURRENT_USER\SOFTWARE\Intel\
{random}
{random} = "{hex values}" =
HKEY_CLASSES_ROOT\WbemScripting.SWbemLastError\CurVer\
{random}
{random} = "{hex values}" =
It adds the following registry keys as part of its installation routine:
HKEY_CURRENT_USER\SOFTWARE\Intel\
{random}
HKEY_CLASSES_ROOT\WbemScripting.SWbemLastError\CurVer\
{random}
Backdoor Routine
This backdoor executes the following command(s) from a remote malicious user:
- Download and execute other files
- Update itself
- Download configuration file
- Delete files
- Uninstall itself
It connects to the following URL(s) to send and receive commands from a remote malicious user:
- http://{BLOCKED}ov.biz/rtl/cef.php
- http://{BLOCKED}0.com/rtl/cef.php
- http://{BLOCKED}ov.biz/rtl/sign.php
- http://{BLOCKED}0.com/rtl/sign.php
Download Routine
This backdoor saves the files it downloads using the following names:
- %User Temp%\{random}.tmp
(Note: %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.)
Information Theft
This backdoor injects itself into the following web browsers to monitor searches made by the user on the following search engines:
- iexplore.exe
- firefox.exe
It retrieves the following information from the affected system:
- Machine GUID
- OS Installation date
- OS version
- Volume information
- Computer Name
Other Details
This backdoor connects to the following URL(s) to check for an Internet connection:
- http://download.windowsupdate.com/
- http://windowsupdate.microsoft.com/
It requires its main component to successfully perform its intended routine.
NOTES:
This backdoor checks if it is executed using the following process:
- svchost.exe
- explorer.exe
- rundll32.exe
SOLUTION
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
Restart in Safe Mode
Step 3
Search and delete these components
Step 4
Scan your computer with your Trend Micro product to delete files detected as BKDR_CORKOW.VDH. 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.
NOTES:
The following created registry key(s) cannot be identified by the user since there are no reference values in the created key:
- HKEY_CURRENT_USER\SOFTWARE\Intel\{random}
- HKEY_CLASSES_ROOT\WbemScripting.SWbemLastError\CurVer\{random}
The only way it can be identified is by comparing the present keys with a backup of the system registry.
Note that the said key(s) do not have to be deleted since it won't be harmful to the system.
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