BKDR_RATLD.A

October 09, 2012
 Analysis by: Roland Marco Dela Paz
 ALIASES:

Win32/McRat.A (NOD32)

 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

Infection Channel:

Dropped by other malware, Downloaded from the Internet

This backdoor may be downloaded by other malware/grayware from remote sites.

It runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size:

81,920 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

14 Jun 2012

Arrival Details

This backdoor may be downloaded by the following malware/grayware from remote sites:

  • HTML_OBFUSCA.BCS

It may be downloaded from the following remote sites:

  • http://www.{BLOCKED}mania.it/img/books.cab

Installation

This backdoor s DLL component is injected to the following process(es):

  • McpRoXy.exe
  • svchost.exe

Autostart Technique

This backdoor registers its dropped component as a system service to ensure its automatic execution at every system startup. It does this by creating the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AppMgmt\Parameters
MyStubPath = "{malware path and file name}"

Other System Modifications

This backdoor modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AppMgmt\Parameters
ServiceDll = "%SystemRoot%\System32\appmgmts.dll"

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

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\AppMgmt\Parameters
ServiceDll = "%User Profile%\AppMgmt.dll"

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

Backdoor Routine

This backdoor executes the following command(s) from a remote malicious user:

  • Download file(s)
  • Execute file(s)

It connects to the following websites to send and receive information:

  • {BLOCKED}.{BLOCKED}.117.132

Dropping Routine

This backdoor drops the following files:

  • %User Profile%\AppMgmt.dll - also detected as BKDR_RATLD.A

(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.)

NOTES:

If the user is not an administrator, this backdoor does the drops the file %User Profile%\SoundMax.dll, which is also detected as BKDR_RATLD.A. It then creates the following registry key:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
SoundMax = "Rundll32.exe %User Profile%\SoundMax.dll, Launch"

  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 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\CurrentControlSet\Services\AppMgmt\Parameters
    • MyStubPath = "{malware path and file name}"
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SoundMax = "Rundll32.exe %User Profile%\SoundMax.dll, Launch"

Step 4

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\SYSTEM\ControlSet001\Services\AppMgmt\Parameters
    • From: ServiceDll = %SystemRoot%\System32\appmgmts.dll
      To: ServiceDll = {random values}
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AppMgmt\Parameters
    • From: ServiceDll = %User Profile%\AppMgmt.dll
      To: ServiceDll = {random values}

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_RATLD.A. 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 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_RATLD.A. 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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