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 connects to a website to send and receive information. However, as of this writing, the said sites are inaccessible.
It modifies Internet Explorer security settings. This puts the affected computer at greater risk, as it allows malicious URLs to be accessed by the computer.
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 files:
- %Application Data%\Div\avicap32.dll -> Detected as BKDR_TEAMBOT.DLL
- %Application Data%\Div\cfmon.exe
- %Application Data%\Div\cfmon.lnk
- %Application Data%\Div\tv_w32.dll
- %Application Data%\Div\tv_w32.exe
- %Application Data%\Div\tv_x64.dll
- %Application Data%\Div\installvpn.pg
- %Application Data%\Div\rdw.pg
- %Application Data%\Div\scankey.pg
- %Application Data%\Div\tv.cfg
- %Application Data%\Div\update.pg
- %Application Data%\Div\TeamViewer_Desktop.exe
- %Application Data%\Div\TeamViewer_Resource_en.dll
- %Application Data%\Div\x64\install64.exe
- %Application Data%\Div\x64\teamviewervpn.sys
- %Application Data%\Div\x64\TeamViewerVPN.inf
- %Application Data%\Div\x64\teamviewervpn.cat
- %Application Data%\Div\x86\install.exe
- %Application Data%\Div\x86\teamviewervpn.sys
- %Application Data%\Div\x86\TeamViewerVPN.inf
- %Application Data%\Div\x86\teamviewervpn.cat
- %User Temp%\{random filename 1}
- %User Temp%\{random filename 2}
- %User Temp%\{random filename 3}.jpg
- %User Temp%\nst{random}.tmp\{random filename 4}
- %User Temp%\nst{random}.tmp\System.dll
- %User Temp%\nst{random}.tmp\nsExec.dll
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
It creates the following folders:
- %Application Data\Div
- %User Temp%\nst{random}.tmp
(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
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
cfmon = C:\Documents and Settings\dyituser_xp32\Application Data\Div\cfmon.exe
Backdoor Routine
This backdoor connects to the following websites to send and receive information:
- http://{BLOCKED}aamfg.info/gfblegh/update.php?id={unique ID}&stat={value}
However, as of this writing, the said sites are inaccessible.
Web Browser Home Page and Search Page Modification
This backdoor modifies Internet Explorer zone settings.
NOTES:
This backdoor can execute the following commands which is received over HTTPS:
- Connects to a specified host server
- Download and execute component files
- Download configuration and updates
- Download updated copy of itself
- Maintains the connection
- Steals information
- Terminates the connection
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
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
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, Windows 7, and Windows Server 2008 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.
• For Windows 8, Windows 8.1, and Windows Server 2012 users
- Access the Charms bar by moving your mouse pointer to the upper right corner of the screen.
- Move your mouse pointer down and click Settings>Change your PC Settings.
- In the left panel, click General.
- In the right panel, scroll down to the bottom to find the Advanced startup section, then click the Restart now button and wait for the system to restart.
- In the Advanced Startup menu, click Troubleshoot>Advanced Options>Startup Settings>Restart and wait for the system to restart.
- In the Startup Settings menu, press 4 to enable safe mode.
Step 4
Remove the malware/grayware file dropped/downloaded by BKDR_TEAMBOT.DLL. (Note: Please skip this step if the threat(s) listed below have already been removed.)
Step 5
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
- cfmon = C:\Documents and Settings\dyituser_xp32\Application Data\Div\cfmon.exe
To delete the registry value this malware created:
- Open Registry Editor. To do this:
» For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run, type regedit in the text box provided, and then press Enter.
» For Windows Vista, Windows 7, and Windows Server 2008 users, click the Start button, type regedit in the Search input field then press Enter.
» For Windows 8, Windows 8.1, and Windows Server 2012 users, right-click on the lower left corner of the screen, click Run, type regedit in the text box provided, and then press Enter. - In the left panel of the Registry Editor window, double-click the following:
HKEY_LOCAL_MACHINE>Software>Microsoft>Windows>CurrentVersion>Run - In the right panel, locate and delete the entry:
cfmon = C:\Documents and Settings\dyituser_xp32\Application Data\Div\cfmon.exe - Close Registry Editor.
Step 6
Search and delete these folders
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Please make sure you check the
Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
- %Application Data\Div
- %User Temp%\nst{random}.tmp
To delete malware/grayware/spyware folders:
For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
- In the File name* input box, type:
- %Application Data\Div
- %User Temp%\nst{random}.tmp
- In the Look In drop-down list, select My Computer, then press Enter.
- Once located, select the folder then press SHIFT+DELETE to permanently delete the folder.
- Repeat steps 2 to 4 for the remaining folders:
- %Application Data\Div
- %User Temp%\nst{random}.tmp
*Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).
For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:
- Open a Windows Explorer window.
- For Windows Vista, 7, and Server 2008 users, click Start>Computer.
- For Windows 8, 8.1, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
- In the Search Computer/This PC input box, type:
- %Application Data\Div
- %User Temp%\nst{random}.tmp
- Once located, select the file then press SHIFT+DELETE to permanently delete the folder.
- Repeat steps 2-3 for the remaining folders:
- %Application Data\Div
- %User Temp%\nst{random}.tmp
*Note: Read the following Microsoft page if these steps do not work on Windows 7.
Step 7
Search and delete these files
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There may be some files 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.
- %Application Data%\Div\avicap32.dll
- %Application Data%\Div\cfmon.exe
- %Application Data%\Div\cfmon.lnk
- %Application Data%\Div\tv_w32.dll
- %Application Data%\Div\tv_w32.exe
- %Application Data%\Div\tv_x64.dll
- %Application Data%\Div\installvpn.pg
- %Application Data%\Div\rdw.pg
- %Application Data%\Div\scankey.pg
- %Application Data%\Div\tv.cfg
- %Application Data%\Div\update.pg
- %Application Data%\Div\TeamViewer_Desktop.exe
- %Application Data%\Div\TeamViewer_Resource_en.dll
- %Application Data%\Div\x64\install64.exe
- %Application Data%\Div\x64\teamviewervpn.sys
- %Application Data%\Div\x64\TeamViewerVPN.inf
- %Application Data%\Div\x64\teamviewervpn.cat
- %Application Data%\Div\x86\install.exe
- %Application Data%\Div\x86\teamviewervpn.sys
- %Application Data%\Div\x86\TeamViewerVPN.inf
- %Application Data%\Div\x86\teamviewervpn.cat
- %User Temp%\{random filename 1}
- %User Temp%\{random filename 2}
- %User Temp%\{random filename 3}.jpg
- %User Temp%\nst{random}.tmp\{random filename 4}
- %User Temp%\nst{random}.tmp\System.dll
- %User Temp%\nst{random}.tmp\nsExec.dll
To delete malware/grayware files:
For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search....
- In the File name* input box, type
- %Application Data%\Div\avicap32.dll
- %Application Data%\Div\cfmon.exe
- %Application Data%\Div\cfmon.lnk
- %Application Data%\Div\tv_w32.dll
- %Application Data%\Div\tv_w32.exe
- %Application Data%\Div\tv_x64.dll
- %Application Data%\Div\installvpn.pg
- %Application Data%\Div\rdw.pg
- %Application Data%\Div\scankey.pg
- %Application Data%\Div\tv.cfg
- %Application Data%\Div\update.pg
- %Application Data%\Div\TeamViewer_Desktop.exe
- %Application Data%\Div\TeamViewer_Resource_en.dll
- %Application Data%\Div\x64\install64.exe
- %Application Data%\Div\x64\teamviewervpn.sys
- %Application Data%\Div\x64\TeamViewerVPN.inf
- %Application Data%\Div\x64\teamviewervpn.cat
- %Application Data%\Div\x86\install.exe
- %Application Data%\Div\x86\teamviewervpn.sys
- %Application Data%\Div\x86\TeamViewerVPN.inf
- %Application Data%\Div\x86\teamviewervpn.cat
- %User Temp%\{random filename 1}
- %User Temp%\{random filename 2}
- %User Temp%\{random filename 3}.jpg
- %User Temp%\nst{random}.tmp\{random filename 4}
- %User Temp%\nst{random}.tmp\System.dll
- %User Temp%\nst{random}.tmp\nsExec.dll
- 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.
*Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).
For Windows Vista, Windows 7, Windows Server 2008, Windows 8, Windows 8.1, and Windows Server 2012:
- Open a Windows Explorer window.
- For Windows Vista, 7, and Server 2008 users, click Start>Computer.
- For Windows 8, 8.1, and Server 2012 users, right-click on the lower left corner of the screen, then click File Explorer.
- In the Search Computer/This PC input box, type:
- %Application Data%\Div\avicap32.dll
- %Application Data%\Div\cfmon.exe
- %Application Data%\Div\cfmon.lnk
- %Application Data%\Div\tv_w32.dll
- %Application Data%\Div\tv_w32.exe
- %Application Data%\Div\tv_x64.dll
- %Application Data%\Div\installvpn.pg
- %Application Data%\Div\rdw.pg
- %Application Data%\Div\scankey.pg
- %Application Data%\Div\tv.cfg
- %Application Data%\Div\update.pg
- %Application Data%\Div\TeamViewer_Desktop.exe
- %Application Data%\Div\TeamViewer_Resource_en.dll
- %Application Data%\Div\x64\install64.exe
- %Application Data%\Div\x64\teamviewervpn.sys
- %Application Data%\Div\x64\TeamViewerVPN.inf
- %Application Data%\Div\x64\teamviewervpn.cat
- %Application Data%\Div\x86\install.exe
- %Application Data%\Div\x86\teamviewervpn.sys
- %Application Data%\Div\x86\TeamViewerVPN.inf
- %Application Data%\Div\x86\teamviewervpn.cat
- %User Temp%\{random filename 1}
- %User Temp%\{random filename 2}
- %User Temp%\{random filename 3}.jpg
- %User Temp%\nst{random}.tmp\{random filename 4}
- %User Temp%\nst{random}.tmp\System.dll
- %User Temp%\nst{random}.tmp\nsExec.dll
- 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 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_TEAMBOT.DLL. 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 9
Reset Internet security settings
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To reset Internet security settings:
- Close all Internet browser windows.
- Open Control Panel. To do this:
• On Windows 2000
Click Start>Settings>Control Panel
• On Windows XP, Server 2003, Vista, and 7
Click Start>Control Panel - Double-click Internet Options.
- In the Internet Properties window, click the Security tab.
- For each Web content zone, click on the Default Level button to set each zone to the default setting.
- Click OK.
