BKDR_XTRAT.BW
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Backdoor
Destructiveness: No
Encrypted:
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.
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:
- %Windows%\Server\server.exe
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
It creates the following folders:
- %Windows%\Server
(Note: %Windows% is the Windows folder, which is usually C:\Windows.)
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
server = "%Windows%\Server\server.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
server = "%Windows%\Server\server.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{8562F781-B0S8-I71H-33AY-I155A7K2E451}
StubPath = "%Windows%\Server\server.exe restart"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{8562F781-B0S8-I71H-33AY-I155A7K2E451}
StubPath = "%Windows%\Server\server.exe"
Other System Modifications
This backdoor deletes the following files:
- %User Profile%\Windows\gs2mfB5.xtr
(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.)
It adds the following registry keys:
HKEY_CURRENT_USER\SOFTWARE\gs2mfB5
HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{8562F781-B0S8-I71H-33AY-I155A7K2E451}
It adds the following registry entries:
HKEY_CURRENT_USER\Software\gs2mfB5
ServerStarted = "12/3/2013 8:54:59 AM"
HKEY_CURRENT_USER\Software\gs2mfB5
InstalledServer = "%Windows%\Server\server.exe"
Dropping Routine
This backdoor drops the following files:
- %User Profile%\Windows\gs2mfB5.cfg
(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.)
Other Details
This backdoor connects to the following possibly malicious URL:
- http://{BLOCKED}0.1:81/1234567890.functions
This report is generated via an automated analysis system.
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
- gs2mfB5
- In HKEY_LOCAL_MACHINE\Software\Microsoft\Active Setup\Installed Components
- {8562F781-B0S8-I71H-33AY-I155A7K2E451}
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- server = "%Windows%\Server\server.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- server = "%Windows%\Server\server.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{8562F781-B0S8-I71H-33AY-I155A7K2E451}
- StubPath = "%Windows%\Server\server.exe restart"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{8562F781-B0S8-I71H-33AY-I155A7K2E451}
- StubPath = "%Windows%\Server\server.exe"
- In HKEY_CURRENT_USER\Software\gs2mfB5
- ServerStarted = "12/3/2013 8:54:59 AM"
- In HKEY_CURRENT_USER\Software\gs2mfB5
- InstalledServer = "%Windows%\Server\server.exe"
Step 5
Search and delete this file
- %User Profile%\Windows\gs2mfB5.cfg
Step 6
Search and delete this folder
- %Windows%\Server
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_XTRAT.BW. 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
Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.
- %User Profile%\Windows\gs2mfB5.xtr
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