TROJ_CONHOOK.AD
Trojan:Win32/Conhook.P (Microsoft); Downloader.a!brm (McAfee); Downloader (Symantec); Trojan-Downloader.Win32.ConHook.dma (Kaspersky); Trojan-Downloader.Win32.ConHook.gen (Sunbelt); Trojan.Downloader.ConHook.AI (FSecure)
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Trojan
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
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 modifies files, disabling programs and applications from properly running.
TECHNICAL DETAILS
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 registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{8e1c1bef-14c5-419e-9ee5-00366c3c69eb}
Other System Modifications
This Trojan modifies the following files:
- %System Root%\ntldr
(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)
It adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DNIdent
HKEY_LOCAL_MACHINE\Software\Microsoft\
aff38ecca6
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mllame
HKEY_CLASSES_ROOT\CLSID\{8e1c1bef-14c5-419e-9ee5-00366c3c69eb}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{8e1c1bef-14c5-419e-9ee5-00366c3c69eb}\InprocServer32
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mllame
Asynchronous = "0"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mllame
Dllname = "mllame.dll"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mllame
Impersonate = "0"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mllame
Startup = "NotifyStartup"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\mllame
Shutdown = "NotifyShutdown"
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{8e1c1bef-14c5-419e-9ee5-00366c3c69eb}\InprocServer32
ThreadingModel = "Free"
It deletes the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
DFC
HKEY_CURRENT_USER\Software\Microsoft\
DFC
Dropping Routine
This Trojan drops the following files:
- %System%\mllame.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.)
This report is generated via an automated analysis system.
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
Close all opened browser windows
Step 3
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\SOFTWARE\Microsoft
- DNIdent
- In HKEY_LOCAL_MACHINE\Software\Microsoft
- aff38ecca6
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
- mllame
- In HKEY_CLASSES_ROOT\CLSID
- {8e1c1bef-14c5-419e-9ee5-00366c3c69eb}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{8e1c1bef-14c5-419e-9ee5-00366c3c69eb}
- InprocServer32
Step 4
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\Windows NT\CurrentVersion\Winlogon\Notify\mllame
- Asynchronous = "0"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mllame
- Dllname = "mllame.dll"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mllame
- Impersonate = "0"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mllame
- Startup = "NotifyStartup"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\mllame
- Shutdown = "NotifyShutdown"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{8e1c1bef-14c5-419e-9ee5-00366c3c69eb}\InprocServer32
- ThreadingModel = "Free"
Step 5
Search and delete this file
- %System%\mllame.dll
Step 6
Scan your computer with your Trend Micro product to delete files detected as TROJ_CONHOOK.AD. 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 7
Restore deleted/modified files and/or registry entries from backup
*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- %System Root%\ntldr
Step 8
Restore these deleted registry keys/values from backup
*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.
- In HKEY_LOCAL_MACHINE\Software\Microsoft
- DFC
- In HKEY_CURRENT_USER\Software\Microsoft
- DFC
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