BKDR_PHDET.AR

October 13, 2012
 ALIASES:

Backdoor:Win32/Phdet.gen!A (Microsoft); Generic BackDoor!d2f (McAfee); Trojan.Gen.2 (Symantec); PAK:UPX (Kaspersky); Trojan.Win32.Kryptik.vke (v) (Sunbelt); Trojan.Generic.KDV.408569 (FSecure)

 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.

  TECHNICAL DETAILS

File Size:

37,888 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

03 Jun 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 drops the following copies of itself into the affected system:

  • %System%\mssrv32.exe

(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.)

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\msupdate

Other System Modifications

This backdoor adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
ImagePath = "%System%\mssrv32.exe"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
DisplayName = "Microsoft security update service"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
Description = "This service downloading and installing Windows security updates"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\msupdate
Type = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AFD\Parameters
DisableRawSecurity = "1"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://sharp.{BLOCKED}r.ru115566335544/stat.php

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
    • msupdate

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\msupdate
    • ImagePath = "%System%\mssrv32.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\msupdate
    • DisplayName = "Microsoft security update service"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\msupdate
    • Description = "This service downloading and installing Windows security updates"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\msupdate
    • ObjectName = "LocalSystem"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\msupdate
    • Start = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\msupdate
    • ErrorControl = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\msupdate
    • Type = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AFD\Parameters
    • DisableRawSecurity = "1"

Step 5

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