BKDR_PCLIENT.AE
Backdoor:Win32/PcClient.CL (Microsoft); BackDoor-CEP.gen.y (McAfee); Trojan.Dropper (Symantec); Backdoor.Win32.PcClient.bal, Backdoor.Win32.PcClient.bal (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Backdoor.Agent.YYF (FSecure)
Windows 2000, Windows XP, Windows Server 2003
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.
TECHNICAL DETAILS
56,135 bytes
EXE
Yes
19 Apr 2012
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.
Autostart Technique
This backdoor 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\SysmonLog\Parameters
Other System Modifications
This backdoor adds the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Services\SysmonLog\Parameters
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\
Services\SysmonLog\Parameters
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
SysmonLog = "SysmonLog"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SysmonLog\Parameters
ServiceDll = "%SystemRoot%\System32\SysmonLog.dll"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Services\SysmonLog\Parameters
ServiceDll = "%SystemRoot%\System32\SysmonLog.dll"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\
Services\SysmonLog\Parameters
ServiceDll = "%SystemRoot%\System32\SysmonLog.dll"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\
Services\SysmonLog
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\
Services\SysmonLog
Description = "Performance Logs and Alerts Service"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SysmonLog
Start = "2"
(Note: The default value data of the said registry entry is 3.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SysmonLog
Description = "Performance Logs and Alerts Service"
(Note: The default value data of the said registry entry is Collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. If this service is stopped, performance information will not be collected. If this service is disabled, any services that explicitly depend on it will fail to start..)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Services\SysmonLog
Start = "2"
(Note: The default value data of the said registry entry is 3.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\
Services\SysmonLog
Description = "Performance Logs and Alerts Service"
(Note: The default value data of the said registry entry is Collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. If this service is stopped, performance information will not be collected. If this service is disabled, any services that explicitly depend on it will fail to start..)
Dropping Routine
This backdoor drops the following files:
- %System%\SysmonLog.dll
- %System%\drivers\SysmonLog.sys
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
This report is generated via an automated analysis system.
SOLUTION
9.200
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
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\SYSTEM\CurrentControlSet\Services\SysmonLog
- Parameters
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\SysmonLog
- Parameters
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\SysmonLog
- Parameters
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\SvcHost
- SysmonLog = "SysmonLog"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SysmonLog\Parameters
- ServiceDll = "%SystemRoot%\System32\SysmonLog.dll"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\SysmonLog\Parameters
- ServiceDll = "%SystemRoot%\System32\SysmonLog.dll"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\SysmonLog\Parameters
- ServiceDll = "%SystemRoot%\System32\SysmonLog.dll"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\SysmonLog
- Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet003\Services\SysmonLog
- Description = "Performance Logs and Alerts Service"
Step 5
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SysmonLog
- From: Start = "2"
To: Start = ""3""
- From: Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SysmonLog
- From: Description = "Performance Logs and Alerts Service"
To: Description = ""Collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. If this service is stopped, performance information will not be collected. If this service is disabled, any services that explicitly depend on it will fail to start.""
- From: Description = "Performance Logs and Alerts Service"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\SysmonLog
- From: Start = "2"
To: Start = ""3""
- From: Start = "2"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\SysmonLog
- From: Description = "Performance Logs and Alerts Service"
To: Description = ""Collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. If this service is stopped, performance information will not be collected. If this service is disabled, any services that explicitly depend on it will fail to start.""
- From: Description = "Performance Logs and Alerts Service"
Step 6
Search and delete these components
- %System%\SysmonLog.dll
- %System%\drivers\SysmonLog.sys
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_PCLIENT.AE. 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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