WORM_SILLY.IFX

 Analysis by: Sabrina Lei Sioting

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via removable drives

This Worm arrives via removable drives.

It modifies certain registry entries to hide file extensions.

It drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

It logs a user's keystrokes to steal information.

It sends gathered information to a predetermined email address using its own Simple Mail Transfer Protocol (SMTP) engine.

  TECHNICAL DETAILS

File Size:

107,008 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Jul 2011

Payload:

Drops files, Steals information

Arrival Details

This Worm arrives via removable drives.

Installation

This Worm drops the following copies of itself into the affected system and executes them:

  • %System%\Important\svchost.exe

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

It creates the following folders:

  • %System%\Important

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

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
svchost = %System%\Important\svchost.exe

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
svchost = %System%\Important\svchost.exe

Other System Modifications

This Worm modifies the following registry entries to hide files with Hidden attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

(Note: The default value data of the said registry entry is 1.)

It modifies the following registry entries to hide file extensions:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
HideFileExt = 1

(Note: The default value data of the said registry entry is 0.)

Propagation

This Worm drops copies of itself in removable drives. These dropped copies use the names of the folders located on the said drives for their file names.

Dropping Routine

This Worm drops the following file(s), which it uses for its keylogging routine:

  • %System%\Important\log.txt

(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Information Theft

This Worm logs a user's keystrokes to steal information.

Stolen Information

This Worm sends gathered information to a predetermined email address using its own Simple Mail Transfer Protocol (SMTP) engine.

NOTES:

It sets the attributes of its dropped folder and files to Hidden.

It uses the process "explorer.exe" to open the original folder where the file name is used for its dropped copy in the removable drive. This routine is to trick the user that its is a folder they are opening.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.274.05

FIRST VSAPI PATTERN DATE:

08 Jul 2011

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 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\CurrentVersion\Run
    • svchost ="%system%\Important\svchost.exe"
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • svchost = "%system%\Important\svchost.exe"

Step 4

Restore this modified 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\Explorer\Advanced
    • From: Hidden = 2
    • To: Hidden = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: HideFileExt = 1
    • To: HideFileExt = 0

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.
%system%\Important

Step 6

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