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Trend Micro has flagged this threat as noteworthy due to the increased potential for damage, propagation, or both, that it possesses.
To get a one-glance comprehensive view of the behavior of this Worm, refer to the Threat Diagram shown below.
This worm arrives via removable drives.
It exploits software vulnerabilities to propagate to other computers across a network.
It hides files, processes, and/or registry entries.
This worm drops the following component file(s):
(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)
This worm drops the following copy(ies) of itself in all removable drives:
It exploits the following software vulnerabilities to propagate to other computers across a network:
This worm exploits this vulnerability in the Windows Shell by calling the StartDocPrinter procedure in order to impersonate the Printer Spooler service to create the file WINSTA.EXE on the Windows system folder of a target machine. It also sends a second file named sysnullevnt.mof and saves it as %System%\wbem\mof. It is automatically registered to the Windows Management Instrumentation then it executes WINSTA.EXE. The said .MOF file also registers an event that deletes its duplicate in the %System%\wbem\mof\good and WINSTA.EXE once the said executable is terminated.
By sending specially crafted RPC requests, this worm can send and execute a copy of itself into a vulnerable system.
(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)
This worm connects to the following URL(s) to send and receive commands from a remote malicious user:
This worm hides files, processes, and/or registry entries.
This worm sends the gathered information via HTTP POST to the following URL:
This worm connects to the following URL(s) to check for an Internet connection:
It does the following:
The server uses dynamic port mapping when listening to a client. Using these functions, two affected systems can communicate with each other and update a copy of this worm if one of them is not updated.
Note that the number of export functions of the modified S7OTBXDX.DLL has 109, while the original .DLL only has 80.
The following are the 16 export functions being intercepted by the NEWS7OTBXDX.DLL.
These functions are used to access, read, write, and delete code blocks on the PLC. By intercepting these functions, this worm can modify the data sent to and from the Programmable Logic Controller (PLC).
Using SQL commands, it is capable of doing the following:
It also creates the file S7HKIMDB.DLL which serves as the decryptor of XUTILS\listen\xr000000.mdx in all folders found under \hOmSave7 in the Simatic Projects folder.
For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.
Remove malware files dropped/downloaded by WORM_STUXNET.A
Identify and delete files detected as WORM_STUXNET.A using the Recovery Console
To identify and delete of malware/grayware files:
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.
To delete the registry key this malware/grayware created:
Search and delete these files
To delete malware/grayware component files:
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_STUXNET.A. 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.
Download and apply this security patch Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.
Note: To identify STUXNET-infected systems within a network, administrators can use Trend Micro's special STUXNET Scanner Tool. For more details, download and extract the package and refer to the tool's incorporated text file.
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