This backdoor may be unknowingly downloaded by a user while visiting malicious websites.
It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.
Arrival Details
This backdoor may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This backdoor drops the following copies of itself into the affected system:
(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)
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
Windows Host = "%System%\winhost.exe"
Backdoor Routine
This backdoor opens the following port(s) where it listens for remote commands:
It executes the following commands from a remote malicious user:
- whatsismyip - sends IP address of infected machine
- whatami - sends the message "you are a loser"
- version - sends the malware version
- cpuinfo - sends malware version, OS version, Path of Windows Directory, Username, CPU Speed, CPU Type
- getdrives - display drives including their drive types (removable, fixed, cd-rom and etc.)
- listdir {file path} - display file directories
- send file {file path} - uploads file to the C&C server
- get file {file path} - downloads file to the C&C server
- shutdown - turn off computer
- restart - reboot computer
- exe_hid {file path} - execute file with isShown value = 0
- exe_sho {file path} - execute file with isShown value = 1
- fil_del {file path} - delete file
- fil_rename {file path} - rename file
- fil_mov {file path} - move file
- fil_copy {file path} - copy file
- okgo - send portion of the malware code to C&C server
It connects to the following websites to send and receive information:
- http://{BLOCKED}s.{BLOCKED}s.co.uk/retan/log.php
It posts the following information to its command and control (C&C) server:
- Malware version
- Malware password
- Port Number
As of this writing, the said servers are currently inaccessible.
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, 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 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
- Windows Host = "%System%\winhost.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:
Windows Host = "%System%\winhost.exe" - Close Registry Editor.
Step 4
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.
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
- 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:
- 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 BKDR_PSYRAT.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.
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