Analysis by: Kiyoshi Obuchi

ALIASES:

VirTool:Win32/CeeInject.gen!FZ (Microsoft), W32/IRCBot.worm.f (McAfee), W32/Slenfb-Gen (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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: Downloaded from the Internet, Dropped by other malware, Via physical/removable drives

This Worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It executes commands from a remote malicious user, effectively compromising the affected system.

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 142,848 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 09 Feb 2012
Payload: Compromises system security, Connects to URLs/IPs, Terminates processes

Arrival Details

This Worm arrives via removable drives.

It 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:

  • %System%\igfxdt86.exe (with Admin Rights)
  • %User Profile%\Network\igfxdt86.exe (without Admin Rights)
  • %Windows%\SysWow64\ igfxdt86.exe ( with 64 bit Admin Rights)

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It creates the following folders:

  • %User Profile%\Network - (without Admin Rights)

(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)

It injects codes into the following process(es):

  • explorer.exe

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Intel Wifi Protocal = "%System%\igfxdt86.exe" (with Admin Rights)

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Intel Wifi Protocal = "%User Profile%\Network\igfxdt86.exe" (without Admin Rights)

Other System Modifications

This Worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AppCompatFlags\
Layers
%System%\igfxdt86.exe = "DisableNXShowUI" (with Admin Rights)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%System%\igfxdt86.exe = "%System%\igfxdt86.exe:*:Enabled:Intel Wifi Protocal (with Admin Rights)

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\igfxdt86.exe = "%System%igfxdt86.exe:*:Enabled:Intel Wifi Protocal" (with Admin Rights)

HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%User Profile%\Network\igfxdt86.exe = "%User Profile%\Network\igfxdt86.exe:*:Enabled:Intel Wifi Protocal" (without Admin Rights)

HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Profile%\Network\igfxdt86.exe = "%User Profile%\Network\igfxdt86.exe:*:Enabled:Intel Wifi Protocal" (without Admin Rights)

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\AppCompatFlags\
Layers
%User Profile%\Network\igfxdt86.exe = "DisableNXShowUI" (without Admin Rights)

Propagation

This Worm drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

The said .INF file contains the following strings:

[Autorun]
open=bootdev-p49682.x32
icon=%windir%\system32\SHELL32.dll,3
action=Browse the contents of the drive.
shell\open=Open
shell\open\command=Sysmount.{GUID}\bootdev-p49682.x32
shell\open\default=1
useautoplay=1

Backdoor Routine

This Worm connects to any of the following IRC server(s):

  • http://j52.coax-{BLOCKED}-{BLOCKED}.su
  • http://j65.coax-{BLOCKED}-{BLOCKED}.su
  • http://j30.bull-{BLOCKED}-{BLOCKED}.su
  • http://j13.bull-{BLOCKED}-{BLOCKED}.su
  • http://j27.bull-{BLOCKED}-{BLOCKED}.su
  • http://j49.coax-{BLOCKED}-{BLOCKED}.su

It executes the following commands from a remote malicious user:

  • Create/Open/Delete Files
  • Create/Terminate Process
  • Download/Upload files
  • Join IRC

Process Termination

This Worm terminates the following processes if found running in the affected system's memory:

  • TEATIMER.EXE
  • MRT.EXE
  • MRTSTUB.EXE
  • HIJACKTHIS.EXE
  • MSPENG.EXE
  • MSASCUI.EXE
  • MPCMDRUN.EXE
  • USBGUARD.EXE
  • BILLY.EXE
  • AADRUVE32.EXE

Download Routine

This Worm accesses the following websites to download files:

  • http://vps682.inte{BLOCKED}.su/net/5x2.zip

Other Details

This Worm connects to the following URL(s) to get the affected system's IP address:

  • http://www.whatismyip.org

It does the following:

  • This worm terminates and deletes itself when the following conditions are met:
    • If file name contains any of the following string:
      • sample
      • virus
      • sand-box
      • sandbox
      • malware
      • test
    • If computer name of the affected system is any of the following:
      • VMG-CLIENT
      • MORTE
      • Malekal
      • HOME-OFF-D5F0AC
      • DELL-D3E62F7E26
      • KAKAPROU-6405DA
    • If user names found on the affected system are any of the following:
      • VMG-CLIENT
      • MORTE
      • Malekal
      • HOME-OFF-D5F0AC
      • DELL-D3E62F7E26
      • KAKAPROU-6405DA
      • klasnich
    • This worm enumerates entries from the following registry and check for the following virtual environment:
      • HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Disk\Enum
      • Vmware
      • Vbox
      • Virutual
      • QEMU
    • It checks if it running in a virtual environment by checking if any of the following files are running in memory:
      • vbox
      • vmrsrvc
      • vmware
      • tcpview
      • wireshark.exe
      • regshot.exe
      • procmon.exe
      • filemon.exe
      • regmon.exe
      • procdump.exe
      • cports.exe
      • procexp.exe
      • squid.exe
      • dumpcap.exe
      • sbiectrl.exe
    • It also checks if opened windows or classes contain any of the following:
      • gdkWindowTopLevel, The Wireshark Network Analyzer
      • CNetmonMainFrame, Microsoft Network Monitor 3.3
      • SmartSniff, SmartSniff
      • CurrPorts,CurrPorts
      • TCPViewClass
      • Process Monitor
    • It also checks if the following files exist:
      • %Program Files%\Ethereal\ethereal.html
      • %Program Files%\Microsoft Network Monitor 3\netmon.exe
      • %Program Files%\WinPcap\rpcapd.exe
      • %Program Files%\WireShark\rawshark.exe
  • It uses the following credentials when logging into its IRC server:
    • NICK: {country}|X-218|0|{OS}|{number}
    • USER: XP-SPX
    • PASSWORD: su1c1d3
  • It accesses the following URLs to retrieve encypted backdoor commands:
    • hxxp://{BLOCKED}.{BLOCKED}.35.28/awstats/rdat02.txt
  • This Worm creates the following folders in all removable drives and network drives:
    • {drive letter}:\Sysmount.{GUID}
  • It drops the following copy(ies) of itself in all removable drives and network drives:
    • {drive letter}:\Sysmount.{GUID}\bootdev-p49682.x32

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 11.562.02
FIRST VSAPI PATTERN DATE: 26 Mar 2015
VSAPI OPR PATTERN File: 11.563.00
VSAPI OPR PATTERN Date: 27 Mar 2015

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 WORM_SLENFBOT.LKF using the Recovery Console

[ Learn More ]

Step 3

Identify and terminate files detected as WORM_SLENFBOT.LKF

[ Learn More ]
  1. Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  2. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

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\Windows NT\CurrentVersion\AppCompatFlags\Layers
    • %System%\igfxdt86.exe = "DisableNXShowUI" (with Admin Rights)
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %System%\igfxdt86.exe = "%System%\igfxdt86.exe:*:Enabled:Intel Wifi Protocal
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\igfxdt86.exe = "%System%igfxdt86.exe:*:Enabled:Intel Wifi Protocal" (with Admin Rights)
  • In HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %User Profile%\Network\igfxdt86.exe = "%User Profile%\Network\igfxdt86.exe:*:Enabled:Intel Wifi Protocal" (without Admin Rights)
  • In HKEY_CURRENT_USER\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %User Profile%\Network\igfxdt86.exe = "%User Profile%\Network\igfxdt86.exe:*:Enabled:Intel Wifi Protocal" (without Admin Rights)
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\Layers
    • %User Profile%\Network\igfxdt86.exe = "DisableNXShowUI" (without Admin Rights)
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Intel Wifi Protocal = "%System%\igfxdt86.exe" (with Admin Rights)
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Intel Wifi Protocal = "%User Profile%\Network\igfxdt86.exe" (without Admin Rights)

Step 5

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.
  • %User Profile%\Network
  • {drive letter}:\Sysmount.{GUID}

Step 6

Search and delete AUTORUN.INF files created by WORM_SLENFBOT.LKF that contain these strings

[ Learn More ]
[Autorun] open=bootdev-p49682.x32 icon=%windir%\system32\SHELL32.dll,3 action=Browse the contents of the drive. shell\open=Open shell\open\command=Sysmount.{GUID}\bootdev-p49682.x32 shell\open\default=1 useautoplay=1

Step 7

Scan your computer with your Trend Micro product to delete files detected as WORM_SLENFBOT.LKF. 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 the following Trend Micro Support pages for more information:


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