Analysis by: Mark Joseph Manahan
ALIASES:

Backdoor:Win32/Ursap!rts (Microsot), Generic.dx!sge (McAfee), Win32/Lethic.AA trojan (Eset), Trojan.Gen (Symantec), Trj/Buzus.AH (Panda), Trojan.Win32.Buzus (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • 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: 114,688 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 15 Nov 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 files:

  • C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\desktop.ini

It drops the following copies of itself into the affected system:

  • C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe

It creates the following folders:

  • C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455
  • C:\RECYCLER

Autostart Technique

This backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe"

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Test321 = "C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe"

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.7.66

  SOLUTION

Minimum Scan Engine: 9.300

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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Taskman = "C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe"
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Shell = "C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Test321 = "C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455\fresdg.exe"

Step 4

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.  
  • C:\RECYCLER\S-1-5-21-0243556031-888888379-781863308-1455

Step 5

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