This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It deletes itself after execution.
Arrival Details
This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Autostart Technique
This Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Microsoft(R) System Manager = "%System%\2a6cdd.exe"
Other System Modifications
This Trojan adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Tcpip\Parameters
TcpTimedWaitDelay = "1e"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Tcpip\Parameters
MaxUserPort = "8"
Dropping Routine
This Trojan drops the following files:
- %System%\msvcrt2.dll
- %System%\2a6cdd.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
Other Details
This Trojan deletes itself after execution.
This report is generated via an automated analysis system.
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
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To restart in Safe Mode:
• For Windows 2000 users
- Restart your computer.
- Press F8 when you see the Starting Windows bar at the bottom of the screen.
- Choose the Safe Mode option from the Windows Advanced Options menu then press Enter.
• For Windows XP users
- Restart your computer.
- Press F8 after the Power-On Self Test (POST) routine is done. If the Windows Advanced Options menu does not appear, try restarting then pressing F8 several times when the POST screen appears.
- Choose the Safe Mode option from the Windows Advanced Options menu then press Enter.
• For Windows Server 2003 users
- Restart your computer.
- Press F8 after Windows starts up. If the Windows Advanced Options menu does not appear, try restarting again and pressing F8 several times afterward.
- On the Windows Advanced Option menu, use the arrow keys to select Safe Mode then press Enter.
• For Windows Vista and Windows 7 users
- Restart your computer.
- Press F8 after the Power-On Self Test (POST) routine is done. If the Advanced Boot Options menu does not appear, try restarting and then pressing F8 several times after the POST screen is displayed.
- On the Advanced Boot Options menu, use the arrow keys to select the Safe Mode option, and then press Enter.
Step 3
Delete this registry value
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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
- Microsoft(R) System Manager = "%System%\2a6cdd.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Tcpip\Parameters
To delete the registry value this malware/grayware created:
- Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
- In the left panel, double-click the following:
HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows>CurrentVersion>Run - In the right panel, locate and delete the entry:
Microsoft(R) System Manager = "%System%\2a6cdd.exe" - In the left panel, double-click the following:
HKEY_LOCAL_MACHINE>SYSTEM>ControlSet001>Services>Tcpip>Parameters - In the right panel, locate and delete the entry:
TcpTimedWaitDelay = "1e" - Again In the right panel, locate and delete the entry:
MaxUserPort = "8" - Close Registry Editor.
Step 4
Search and delete these components
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There may be some components 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.
- %System%\msvcrt2.dll
- %System%\2a6cdd.exe
To manually delete a malware/grayware component from an affected system:
• For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search....
- In the Named input box, type:
- %System%\msvcrt2.dll
- %System%\2a6cdd.exe
- In the Look In drop-down list, select My Computer then press Enter.
- Once located, select the file then press SHIFT+DELETE to delete it.
- Repeat the said steps for all files listed.
• For Windows Vista and Windows 7 users:
- Click Start>Computer.
- In the Search input box, type:
- %System%\msvcrt2.dll
- %System%\2a6cdd.exe
- Once located, select the file then press SHIFT+DELETE to delete it.
- Repeat the said steps for all files listed.
*Note: Read the following Microsoft page if these steps do not work on Windows 7.
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DONBOT.AH. 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.
