Analysis by: Erika Bianca Mendoza
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • 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 requires its main component to successfully perform its intended routine.

  TECHNICAL DETAILS

File Size: 229,376 bytes
File Type: OCX
Memory Resident: Yes
Initial Samples Received Date: 19 Apr 2011
Payload: Drops files, Connects to URLs/Ips, Downloads files, Compromises system security

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}

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 in the system.

It may attach itself to the following processes:
  • *\explorer.exe
  • *\intern*\iexplore.exe
  • *\firefox.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}3.{BLOCKED}ages.net
Once successfully connected, it may send a list of URLs to be monitored, usually related to financial institutions and search engines. During testing, the following URLs were monitored:
  • https://*chase.com*
  • *http:*bing.*q=*
  • *http:*search.yahoo.*p=*
  • *http:*google.*q=*

It logs the obtained information to one of the dropped .DAT files.

It 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
It performs the following action after a connection is established:
  • Open, Create, Rename, Delete files/registries
  • Scan drives
  • Shutdown affected machine
  • Shutdown, restart, or respawn itself
  • Terminate processes
It accesses the following URL via HTTP GET to download an updated copy of the malware:
  • {BLOCKED}3.{BLOCKED}ages.net/image.cgi?1

  SOLUTION

Minimum Scan Engine: 8.900
FIRST VSAPI PATTERN FILE: 7.930.07
FIRST VSAPI PATTERN DATE: 27 Mar 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.HB

Step 3

Delete the created random CLSID key

[ Learn More ]

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

[ Learn More ]

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}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers
    • {malware file name}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers
    • {random file name 3}

Step 5

Search and delete this file

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.
  • %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.HB

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files in the search result.

Step 7

Scan your computer with your Trend Micro product to delete files detected as BKDR_AFCORE.HB. 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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