BKDR_PCCLIENT.OLL
Backdoor:Win32/PcClient.ZR (Microsoft); Downloader-BYH (McAfee); Backdoor.Trojan (Symantec); Trojan-GameThief.Win32.Magania.dpvu (Kaspersky); Backdoor.Win32.PcClient (Sunbelt); Could be a Trojan horse Agent (AVG)
Windows
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
79,595 bytes
EXE
Yes
11 Jul 2015
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 adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{8D67835B-44AB-4dc4-A119-350334F31BFE}
stubpath = "%System%\inoavpdfe.exe"
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\PCRatStact
Other System Modifications
This backdoor adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{8D67835B-44AB-4dc4-A119-350334F31BFE}
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\PCRatStact
Type = "12"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
ProgramFilesDir = "%Program Files%"
(Note: The default value data of the said registry entry is %Program Files%.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\SFC
CommonFilesDir = "%Program Files%\Common Files"
(Note: The default value data of the said registry entry is %Program Files%\Common Files.)
It deletes the following registry keys:
HKEY_CURRENT_USER\Software\Microsoft\
Active Setup\Installed Components\{8D67835B-44AB-4dc4-A119-350334F31BFE}
Dropping Routine
This backdoor drops the following files:
- %System%\inoavpdfe.exe
- %System%\syslog.dat
- %User Temp%\36703_res.tmp
(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
Other Details
This backdoor connects to the following possibly malicious URL:
- {BLOCKED}0.1
This report is generated via an automated analysis system.
SOLUTION
9.750
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
- PCRatStact
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
- {8D67835B-44AB-4dc4-A119-350334F31BFE}
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\Active Setup\Installed Components\{8D67835B-44AB-4dc4-A119-350334F31BFE}
- stubpath = "%System%\inoavpdfe.exe"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\PCRatStact
- Type = "12"
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\Control\Session Manager\SFC
- From: ProgramFilesDir = "%Program Files%"
To: ProgramFilesDir = ""%Program Files%""
- From: ProgramFilesDir = "%Program Files%"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\SFC
- From: CommonFilesDir = "%Program Files%\Common Files"
To: CommonFilesDir = ""%Program Files%\Common Files""
- From: CommonFilesDir = "%Program Files%\Common Files"
Step 6
Search and delete these components
- %System%\inoavpdfe.exe
- %System%\syslog.dat
- %User Temp%\36703_res.tmp
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_PCCLIENT.OLL. 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 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_CURRENT_USER\Software\Microsoft\Active Setup\Installed Components
- {8D67835B-44AB-4dc4-A119-350334F31BFE}
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