BKDR_AFCORE.HC
Windows 2000, Windows XP, Windows Server 2003
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This backdoor arrives as a component bundled with malware/grayware packages. It may be unknowingly downloaded by a user while visiting malicious websites.
It is a component of other malware. It may be injected into processes running in memory.
It executes commands from a remote malicious user, effectively compromising the affected system.
It requires its main component to successfully perform its intended routine.
TECHNICAL DETAILS
180,224 bytes
OCX
Yes
21 Apr 2011
Steals information
Arrival Details
This backdoor arrives as a component bundled with malware/grayware packages.
It may be unknowingly downloaded by a user while visiting malicious websites.
Installation
This backdoor drops the following non-malicious files:
- %System%\{random file name 1}.dat
- %System%\{random file name 2}.dat
- %System%\{random file name 3}.dat
- %System%\{random file name 4}.dat
- %Current%\{malware file name}.dat
(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.)
It drops the following copies of itself into the affected system:
- %System%\{random file name 3}.ocx
(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.)
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- Global\{random characters}
- Local\{random characters}
It is a component of other malware.
It may be injected into processes running in memory.
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(Default} = "{malware path and file name}"
HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(Default) = "%System%\{random file name 3}.ocx"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\{malware filename}
DllName = {malware path and filename}
Other System Modifications
This backdoor adds the following registry keys as part of its installation routine:
HKEY_CLASSES_ROOT\CLSID\{random CLSID}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{malware file name}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{random file name 3}
Backdoor Routine
This backdoor executes the following commands from a remote malicious user:
- ADDTO
- DELCOOKIES
- DELFROM
- DISKFLOOD
- DISKUNFLOOD
- EXPORT
- IPHLP
- IPHLPA
- IPHLPF
- LISTCOOKIES
- LSTWND
- MULTICAST
- PERFRM
- RESOLVE
- RESPAWN
- RESTART
- RMOLD
- RUNDLL
- SETCOOKIE
- SETRADIUS
- SETRANGE
- SETSP
- SETSP3
- SETSTR
- SETWND
- SHUTDOWN
- STATS
- UNFREEZE
- UNIFORG
- UNINSTALL
Other Details
This backdoor requires its main component to successfully perform its intended routine.
NOTES:
This file is a component of another malware that may be used to log user activities on the system.
It may attach itself to the following processes:
- *\explorer.exe
- *\intern*\iexplore.exe
- *\firefox.exe
- *\chrome.exe
- *\opera.exe
- *\outlook.exe
- *\outloo*\msimn.exe
It monitors the browsing activities of the user and gathers information entered in websites with the following strings:
- *.nhs.net/*
- *.nhs.uk/*
- *.hilton.*
- *.yahoo.*
- *.google.*
This backdoor connects to the following server via HTTP POST using TCP port 80 to wait for commands coming from a remote user:
- {BLOCKED}ocker.antrexhost.com
It logs the gathered information to one of the dropped .DAT files.
It performs the following actions after a connection is established:
- Open, create, rename, delete files/registries
- Scan drives
- Shutdown affected machine
- Shutdown, restart, or respawn itself
- Terminate processes
SOLUTION
8.900
8.108.08
21 Apr 2011
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_AFCORE.HC
Step 3
Delete the created random CLSID 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.
Step 4
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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
- {malware filename}
- {malware filename}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers
- {malware file name}
- {malware file name}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers
- {random file name 3}
- {random file name 3}
Step 5
Search and delete this file
- %System%\{random file name 1}.dat
- %System%\{random file name 2}.dat
- %System%\{random file name 3}.dat
- %System%\{random file name 4}.dat
Step 6
Search and delete the file detected as BKDR_AFCORE.HC
Step 7
Scan your computer with your Trend Micro product to delete files detected as BKDR_AFCORE.HC. 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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