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BKDR_THOPER.AC

October 13, 2012
 ALIASES:

Trojan.Win32.Generic!BT (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

163,840 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

28 May 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.

Installation

This backdoor creates the following folders:

  • %User Profile%\Microsoft
  • %User Profile%\Microsoft\PDA

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

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\TEST\Parameters

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\Software\CLASSES\
SS\PROXY

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\TEST\Parameters
ServiceDll = "%User Profile%\PDA\TEST.DLL"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\TEST\Parameters
ServiceMain = "ServiceMain"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
LocalService = "Alerter,WebClient,LmHosts,RemoteRegistry,upnphost,SSDPSRV,TEST"

(Note: The default value data of the said registry entry is {random values}.)

Dropping Routine

This backdoor drops the following files:

  • %User Profile%\PDA\TEST.DLL

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://redmil.{BLOCKED}p.biz/update?id=0119ec54
  • http://redmil.{BLOCKED}p.biz/update?id=8432bf7c
  • http://redmil.{BLOCKED}p.biz/update?id=74c80d35
  • http://redmil.{BLOCKED}p.biz/update?id=4a7d6295
  • http://redmil.{BLOCKED}p.biz/update?id=a1faae25
  • http://redmil.{BLOCKED}p.biz/update?id=4d441cdd
  • http://redmil.{BLOCKED}p.biz/update?id=ecdc0ad0

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

Restart in Safe Mode

[ Learn More ]

Step 3

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.

  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\TEST
    • Parameters
  • In HKEY_LOCAL_MACHINE\Software\CLASSES\SS
    • PROXY

Step 4

Delete this registry value

[ 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.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\TEST\Parameters
    • ServiceDll = "%User Profile%\PDA\TEST.DLL"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\TEST\Parameters
    • ServiceMain = "ServiceMain"

Step 5

Restore this modified registry value

[ 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.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • From: LocalService = "Alerter,WebClient,LmHosts,RemoteRegistry,upnphost,SSDPSRV,TEST"
      To: LocalService = ""{random values}""

Step 6

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.
  • %User Profile%\PDA\TEST.DLL

Step 7

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Profile%\Microsoft
  • %User Profile%\Microsoft\PDA

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_THOPER.AC. 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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