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:
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\msimfo32.exe
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It creates the following folders:
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\msimfo32.exe"
Other System Modifications
This backdoor adds the following registry keys:
HKEY_CURRENT_USER\Software\bcrypt
It adds the following registry entries:
HKEY_CURRENT_USER\Software\bcrypt
i = "7d9"
Dropping Routine
This backdoor drops the following files:
- %User Profile%\Application Data\bcrypt.html
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\Desktop.ini
(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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
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
Identify and delete files detected as BKDR_IRCBOT.BXW using either the Startup Disk or Recovery Console
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To identify and delete the malware/grayware file:
• On Windows XP and Server 2003 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Click Start>Run. In the Open input box, type secpol.msc and press Enter.
- In the left panel, double-click Local Policies>Security Options.
- In the right panel, double-click Recovery Console: Allow floppy copy and access to all drives and folders.
- Select Enabled and click OK.
- Insert the Windows Installation CD into the CD drive, then restart your computer.
- When prompted, press any key to boot from the CD.
- On the main menu, type r to go to the Recovery Console.
- Type the number that corresponds to the drive and directory that contains Windows (usually C:\WINDOWS) and press Enter.
- Type the Administrator password and press Enter.
- In the input box, type the following then press Enter:
SET AllowAllPaths = TRUE
del "{malware/grayware path and file name}" - Type exit and press Enter to restart the system normally.
• On Windows Vista and 7 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Insert your Windows Installation DVD in the DVD drive, then Press the restart button.
- When prompted, press any key to boot from the CD.
- Depending on your Windows Installation DVD, you might be required to select the installation language. Then on the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Next, then click Repair your computer.
- Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
- If the Startup Repair window appears, click Cancel, Yes, then Finish.
- In the System Recovery Options window, click Command Prompt.
- In the Command Prompt window, type the following then press Enter:
BootRec.exe /fixmbr
del "{malware/grayware path and file name}" - Type exit and press Enter to close the Command Prompt window.
- Click Restart to restart the system normally.
Step 3
Delete this registry key
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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_CURRENT_USER\Software
To delete the registry key this malware/grayware created:
- Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
- In the left panel, double-click the following:
HKEY_CURRENT_USER>Software - Still in the left panel, locate and delete the key:
bcrypt - Close Registry Editor.
Step 4
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 NT\CurrentVersion\Winlogon
- Taskman = "%System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\msimfo32.exe"
- In HKEY_CURRENT_USER\Software\bcrypt
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 NT>CurrentVersion>Winlogon - In the right panel, locate and delete the entry:
Taskman = "%System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\msimfo32.exe" - In the left panel, double-click the following:
HKEY_CURRENT_USER>Software>bcrypt - In the right panel, locate and delete the entry:
i = "7d9" - Close Registry Editor.
Step 5
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.
- %User Profile%\Application Data\bcrypt.html
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\Desktop.ini
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:
- %User Profile%\Application Data\bcrypt.html
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\Desktop.ini
- 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:
- %User Profile%\Application Data\bcrypt.html
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890\Desktop.ini
- 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 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.
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890
To delete malware/grayware/spyware folders:
- Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
- In the Named input box, type:
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890
- 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:
- %System Root%\RECYCLER
- %System Root%\RECYCLER\S-1-5-21-2845342716-0395791040-577086329-4890
Step 7
Scan your computer with your Trend Micro product to delete files detected as BKDR_IRCBOT.BXW. 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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