TROJ_DELF.ARW


 ALIASES:

Backdoor:Win32/Delf.IV (Microsoft); BackDoor-AWQ.b.gen.o (McAfee); Trojan.KillAV (Symantec); Trojan-Spy.Win32.Delf.eor (Kaspersky); Trojan.Win32.Generic.pak!cobra (Sunbelt); Trojan horse Injector.BS (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This Trojan 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:

182,784 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

11 Jun 2013

Arrival Details

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

Autostart Technique

This Trojan 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\Windowsϵͳ©¶´²¹¶¡\Parameters

Other System Modifications

This Trojan adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Windowsϵͳ©¶´²¹¶¡\Parameters
ServiceDLL = "%SystemRoot%\system32\drivers\etc\K4SUDSnG.dll"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Windowsϵͳ©¶´²¹¶¡
Description = "Windowsϵͳ©¶´²¹¶¡"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = "{random characters}"

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

Dropping Routine

This Trojan drops the following files:

  • %System%\UpZLydaa0N.ini
  • %System%\UpZLydaa0N.del
  • %System%\drivers\etc\K4SUDSnG.dll

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Other Details

This Trojan deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

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\Windowsϵͳ©¶´²¹¶¡
    • Parameters

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\Windowsϵͳ©¶´²¹¶¡\Parameters
    • ServiceDLL = "%SystemRoot%\system32\drivers\etc\K4SUDSnG.dll"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Windowsϵͳ©¶´²¹¶¡
    • Description = "Windowsϵͳ©¶´²¹¶¡"

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • From: netsvcs = "{random characters}"
      To: netsvcs = ""{random values}""

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %System%\UpZLydaa0N.ini
  • %System%\UpZLydaa0N.del
  • %System%\drivers\etc\K4SUDSnG.dll

Step 7

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