BKDR_IDICAF.DL
Backdoor:Win32/Idicaf.gen!B (Microsoft), Generic BackDoor!dkb (McAfee), Backdoor.Win32.Agent.bmsq (Kaspersky)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
Threat Type: Backdoor
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
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 deletes the initially executed copy of itself.
TECHNICAL DETAILS
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%\{malware file name}.dll
- %System%\dllcache\ntmssvc.dll
(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.)
Autostart Technique
This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Irmon
ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Irmon
DisplayName = "Irmon System Services"
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Irmon\Parameters
ServiceDll = "{malware path and file name}"
It adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{random CLSID}
StubPath = "Rundll32.exe {malware path and file name},AXMain"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "Rundll32.exe {malware path and file name},Rundll32Main"
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Irmon
Other System Modifications
This backdoor modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\NtmsSvc
Start = "2"
(Note: The default value data of the said registry entry is 3.)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\NtmsSvc
ErrorControl = "0"
(Note: The default value data of the said registry entry is 1.)
Other Details
This backdoor deletes the initially executed copy of itself
NOTES:
It copies the existing %System%\conime.exe to %System%\eminoc_bd.dll, and %System%\ntmssvc.dll to %System%\ntmssvc.dll.obak as backups. It replaces the existing %System%\ntmssvc.dll with a copy of itself.
It patches %System%\conime.exe to automatically load %System%\{malware file name}.dll whenever it is executed.
SOLUTION
Step 1
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.
Step 2
Scan your computer with your Trend Micro product and note files detected as BKDR_IDICAF.DL
Step 3
Restart in Safe Mode
Step 4
Search and delete the file detected as BKDR_IDICAF.DL
Step 5
Delete this registry value
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\Active Setup\Installed Components\{random CLSID}
- StubPath="Rundll32.exe {malware path and file name},AXMain"
- StubPath="Rundll32.exe {malware path and file name},AXMain"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- {malware file name}="Rundll32.exe {malware path and file name},Rundll32Main"
- {malware file name}="Rundll32.exe {malware path and file name},Rundll32Main"
Step 6
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.
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
- Irmon
- Irmon
Step 7
Restore this modified registry value
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\SYSTEM\CurrentControlSet\Services\NtmsSvc
- From: Start = "2"
To: Start = "3"
- From: Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NtmsSvc
- From: ErrorControl = "0"
To: ErrorControl = "1"
- From: ErrorControl = "0"
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_IDICAF.DL. 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.
NOTES:
Perform the following before restarting in normal mode:
Restoring Files to their Original Location1. Open a Command Prompt window.
- For Windows 2000, Windows XP, and Windows Server 2003 users, click Start > Run. In the Open input box, type cmd, then press Enter.
- For Windows Vista and Windows 7 users, click Start, type cmd in the Search input field, then press Enter.
2. In the Command Prompt window, type the following commands:
3. Close the Command Prompt window by typing the following command:
- exit
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