Threat Description

Scrambler

Details

Aliases: Scrambler, IWorm_Scrambler, I-Worm.Scrambler
Category: Malware
Type: Worm
Platform: W32

Summary



Scrambler is an Internet worm-virus that spreads itself in e-mail attachments, sends its copies to IRC channels, and infects Windows EXE files on the local machine. The worm itself is a Windows PE executable, about 70Kb long and it is written in Microsoft Visual C++.



Removal



Automatic Disinfection

Allow F-Secure Anti-Virus to disinfect the relevant files.

For more general information on disinfection, please see Removal Instructions.



Technical Details



When the worm's file is run for the first time, it creates its dropper (the file with pure worm's code) in the Windows system directory. This file has a random 5-letter name, for example: HIJDE.EXE. The file will be used to send worm copies to Internet and IRC channels later.

Then the worm scans the Windows directory, looks for Windows EXE files and infects them by writing its code to the top of the file. The worm avoids infecting the files with names that begin with any of the following letters: E, P, R, T, W. Then the worm infects all EXE files in the C:\MIRC\DOWNLOAD directory if such directory exists.

Afterward the worm modifies the mIRC client settings to send its copies to IRC channels. It modifies MS Outlook, too, to spread with e-mail messages.

The worm tries to overwrite the SCRIPT.INI file in standard mIRC directories on all drives from C: to F: to modify the mIRC client settings. The worm writes a short script in that file to send its dropper to each user that enters an infected channel.

The worm creates the SCRAMBLER.VBS file in the Windows System directory and writes there a Visual Basic script program which will connect to MS Outlook and send e-mail messages to the first 90 users taken from the MS Outlook address book. Messages that are sent have the worm's dropper as an attachment, the message subject is "Check this out, it's funny!" and the message body is empty. Then the worm spawns that script and as a result, spreads to the Internet.

The worm creates the WINSTART.BAT file in the Windows directory and writes two commands to that file which will clear the screen and display this message when the file is executed:

Today..
 I'm going to scramble your mind..

The worm also creates the SCRAM.SYS file and saves the following text there:

Scrambler
 by Gigabyte

The worm has a dangerous payload - it scans hard drives for MP3 files and corrupts them.


Variant:Scrambler.A (Scooter, I-Worm_Scooter, I-Worm.Scooter, MP3 virus)

Size:166131

This variant of Scrambler worm spreads itself as an attachment to an e-mail message, using Outlook application. The message has the following characteristics:

  Subject:    Faster.. harder.. your PC will run like a scooter!
    Attachment: (random).exe

The attachment has a random, 5 letter file name and the ".exe" extension. This name is randomly generated by the worm upon its first installation to an infected system. The worm itself is a PE executable packed with PECompact file compressor.

When run, the worm copies itself with a random name to \Windows\System\ folder, unpacks from itself SCOOTER.MP3 file that contains a part of a song made by the band "Scooter", creates SCOOTER.SYS file with the following text inside: "Faster.. harder.. scooter!".

It attempts to play the unpacked MP3 file if a compatible MP3 player is found in a system.

The worm replaces SCRIPT.INI file in mIRC installation directory. The new script file makes IRC client to spread the worm to all users of IRC channels where an infected user joins.





Technical Details: F-Secure and AVP teams; September 2000


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