Classification

Category: Malware

Type: Worm

Aliases: Scold.A

Summary


Scold is a basic mass mailer discovered on the 11th of December 2003. It will send simple emails. The worm uses very simple tricks to try to avoid generic and heuristic detection by scrambling obvious text strings.

Removal


Removal of the file suffices to eliminate this threat from the system.

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Technical Details


This worm was written in Visual Basic and packed with UPX. The packed executable has suffered no later modifications to make the unpacking process more difficult.

The size of the packed executable is 28160 bytes. Once unpacked it grows up to 61440 bytes long.

The worm author tried to avoid general detection methods by scrambling the main strings in the worm's code. Some of the text strings are reversed and other are written character by character.

Installation to system

The worm will copy itself to the Windows' System folder as "Warm.scr", whose path will be obtained by means of the GetSpecialFolder Method.

It will add an entry in the Windows Registry under:

[HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run]
"ExeName32"
 

to point to the "Warm.scr" file, so it's run as soon as Windows starts.

Spreading in email.

The subject is one of the following:

When It's Cold Outside She Gives Me Warm Inside
Fw:When It's Cold Outside She Gives Me Warm Inside
Re:When It's Cold Outside She Gives Me Warm Inside
 

The email body will contain text from the following list:

You will love this cute picture.
Enjoy this great picture.
Don't miss this cool picture.
 

Followed by some text like:

Free Online Virus Scan.
No viruses or suspicious files were found in the attached file.
 

The attachment will have the extension ".SCR"

It will send messages to all the addresses in the user's address book. It will also look for addresses in HTML files present in the computer's HD.