BKDR_KULUOZ.VH
Win32/TrojanDownloader.Zortob.B trojan (Eset), TrojanDownloader:Win32/Kuluoz.B (Microsoft), Trojan.Fakeavlock (Symantec)
Windows 2000, Windows XP, Windows Server 2003
![](/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 executes then deletes itself afterward.
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
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 drops the following copies of itself into the affected system:
- %Application Data%\{random}.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 processes:
- svchost.exe
It executes then deletes itself afterward.
It leaves the following text files:
- {Malware Path and Filename}.txt
It injects codes into the following process(es):
- created svchost.exe
Backdoor Routine
This backdoor executes the following commands from a remote malicious user:
- Sleep/Idle (2 minutes)
- Download and execute arbitrary file
- Update and uninstall itself
- Visit URL
It connects to the following websites to send and receive information:
- http://{BLOCKED}.{BLOCKED}.145.174:6667/{generated value}
- http://{BLOCKED}.{BLOCKED}.10.68:8080/{generated value}
- http://{BLOCKED}.{BLOCKED}.178.174:8080/{generated value}
- http://{BLOCKED}.{BLOCKED}.224.202:8080/{generated value}
- http://{BLOCKED}.{BLOCKED}.123.128:8080/{generated value}
- http://{BLOCKED}.{BLOCKED}.203.178:8080/{generated value}
- http://{BLOCKED}.{BLOCKED}.15:8080/{generated value}
- http://{BLOCKED}.{BLOCKED}.135.154:8080/{generated value}
NOTES:
If the malware fails to connect to any of the C&C servers, it creates the following registries:
HKEY_CURRENT_USER\SOFTWARE\{random}
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run {random} = "%Application Data%\{random}.exe"
HKEY_CURRENT_USER\SOFTWARE\{random} {random} = "{hex values}"
The {generated value} is based on user name, Local IP, running debugger, and malware build date and version.
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
Delete this registry key
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
- {random}
- {random}
Step 4
Delete this registry value
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
- {random} = %Application Data%\{random}.exe
- {random} = %Application Data%\{random}.exe
Step 5
Search and delete these components
- {Malware Path and Filename}.txt
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_KULUOZ.VH. 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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