WORM_DELF.TYU

October 04, 2014
 Analysis by: Adrian Cofreros
 ALIASES:

Worm:Win32/Delf.BD(Microsoft),Trojan.Win32.StartPage.azr(Kaspersky),Win32/Delf.NEQ worm(NOD32)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet, Propagates via flashdrives

This worm 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:

425,984 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Sep 2014

Payload:

Drops files, Modifies system registry

Arrival Details

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

  • %Application Data%\{random application}.exe
  • %Windows%\inf\smss.exe
  • %System%\Sexy Girls.scr

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.. %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
NT_Authority = %Application Data%\{random application}.exe

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
FrameWorkService = "%Windows%\inf\smss.exe I'm so ugly, I hate myself and I want to die"

Other System Modifications

This worm adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\DisallowRun

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
DisallowRun = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoRun = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFind = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\DisallowRun
1 = "cmd.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\DisallowRun
2 = "mmc.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\DisallowRun
3 = "rstrui.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\DisallowRun
4 = "regedit.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\DisallowRun
5 = "regedt32.exe"

Propagation

This worm drops copies of itself in network drives such as the following:

  • {Drive Letter}:\{User Name}_Fichiers.exe
  • {Drive Letter}:\{folder name}\{folder name}.exe

It drops the following copy(ies) of itself in all removable drives:

  • {Drive Letter}:\{User Name}_Fichiers.exe
  • {Drive Letter}:\{folder name}\{folder name}.exe

NOTES:

{random application} can be any of the following:

  • smss.exe
  • svchost.exe
  • lsass.exe
  • csrss.exe

This malware restricts the execution of the following files by adding specific registry entries.

  • cmd.exe
  • mmc.exe
  • rstrui.exe
  • regedit.exe
  • regedt32.exe

It drops copy of itself to the subfolders of the directory where the malware has been executed.

Its drop copies of itself has a file icon of a 'folder' which may trick the user on knowing its just a folder and possibly clicking it.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

11.138.03

FIRST VSAPI PATTERN DATE:

09 Sep 2014

VSAPI OPR PATTERN File:

11.139.00

VSAPI OPR PATTERN Date:

10 Sep 2014

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • %Application Data%\{random application}.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • FrameWorkService = "%Windows%\inf\smss.exe I'm so ugly, I hate myself and I want to die"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • DisallowRun = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoFolderOptions = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoRun = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoFind = "1"

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • NT_Authority = "%Application Data%\svchost.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • FrameWorkService = "%Windows%\inf\smss.exe I'm so ugly, I hate myself and I want to die"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • DisallowRun = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoFolderOptions = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoRun = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoFind = "1"

Step 5

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