BKDR_AFCORE.SMA2

 Analysis by: kathleenno

 ALIASES:

Trojan.Gen (Symantec); Backdoor:Win32/Afcore.gen!A (Microsoft); Trojan-PSW.Win32.Qbot.cje (Kaspersky); CoreFlood.dll (Mcafee)

 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 malware is a component of another malware.

It attaches itself to certain processes.

It monitors the browsing activities of the user.

It exectures certain commands from a remote malicious user.

This backdoor may arrive bundled with malware packages as a malware component. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It is a component of other malware.

It opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

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

  TECHNICAL DETAILS

File Size:

173,568 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

27 Mar 2011

Payload:

Drops files, Compromises system security

Arrival Details

This backdoor may arrive bundled with malware packages as a malware component.

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops the following non-malicious files:

  • %System%\{random filename 1}.dat
  • %System%\{random filename 2}.dat
  • %System%\{random filename 3}.dat
  • %System%\{random filename 4}.dat
  • %Current%\{malware filename}.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 filename 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.

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 filename}

HKEY_CLASSES_ROOT\CLSID\{random CLSID}\
InprocServer32
(default) = %System%\{random filename 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 filename}

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
ShellIconOverlayIdentifiers\{random filename 3}

Backdoor Routine

This backdoor opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

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.*
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

  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.SMA2

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 the file detected as BKDR_AFCORE.SMA2

[ 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 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_AFCORE.SMA2. 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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