TROJ_DELF.KNY


 ALIASES:

TrojanSpy:Win32/Delf.EQ (Microsoft); Generic PWS.y (McAfee); Trojan.Littlog (Symantec); Trojan-Downloader.Win32.Delf.koi (Kaspersky); BehavesLike.Win32.Malware.wsc (mx-v) (Sunbelt); KillKAV (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:

17,221 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

30 May 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.

Installation

This Trojan drops the following copies of itself into the affected system:

  • %Windows%\hook_.exe

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

It creates the following folders:

  • %System%\webdav

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

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{2bf41072-b2b1-21c1-b5c1-0305f4155515}
StubPath = "%Windows%\hook_.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
h00k_ = "%Windows%\hook_.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Runservices
h00k_ = "%Windows%\hook_.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "explorer.exe 4DFlowerBox.scr"

(Note: The default value data of the said registry entry is Explorer.exe.)

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{2bf41072-b2b1-21c1-b5c1-0305f4155515}

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Runservices

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Internet Settings
h00k_ = "{malware path and file name}"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
system = "%System%\fontstyles.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
User Shell Folders
Common startup = "%System%\webdav"

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

It deletes the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Active Setup\Installed Components\{2bf41072-b2b1-21c1-b5c1-0305f4155515}

Dropping Routine

This Trojan drops the following files:

  • %Windows%\syxsocks.dll
  • %Windows%\smlogitech.vbs
  • %Windows%\cht.pol
  • %System%\fontstyles.exe
  • %System%\wednav\bslogitech.exe
  • %Windows%\4DFlowerBox.scr

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %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

Identify and delete files detected as TROJ_DELF.KNY using either the Startup Disk or Recovery Console

[ 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\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {2bf41072-b2b1-21c1-b5c1-0305f4155515}
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion
    • Runservices

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\SOFTWARE\Microsoft\Active Setup\Installed Components\{2bf41072-b2b1-21c1-b5c1-0305f4155515}
    • StubPath = "%Windows%\hook_.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • h00k_ = "%Windows%\hook_.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Runservices
    • h00k_ = "%Windows%\hook_.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings
    • h00k_ = "{malware path and file name}"

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\Winlogon
    • system = "%System%\fontstyles.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
    • From: Common startup = "%System%\webdav"
      To: Common startup = ""{random values}""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "explorer.exe 4DFlowerBox.scr"
      To: Shell = ""Explorer.exe""

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.
  • %Windows%\syxsocks.dll
  • %Windows%\smlogitech.vbs
  • %Windows%\cht.pol
  • %System%\fontstyles.exe
  • %System%\wednav\bslogitech.exe
  • %Windows%\4DFlowerBox.scr

Step 7

Search and delete this folder

[ 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.
  • %System%\webdav

Step 8

Scan your computer with your Trend Micro product to delete files detected as TROJ_DELF.KNY. 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 9

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {2bf41072-b2b1-21c1-b5c1-0305f4155515}


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