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 e-mail.
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 e-mail 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.
Detection
F-Secure Anti-Virus detects this worm using generic methods. Exact detection
was published on December 11th, 2003 in update:
[FSAV_Database_Version]
Version=2003-12-11_01
Write-up:
Ero Carrera, December 11th, 2003;
Technical Details:
Ero Carrera, December 11th, 2003;
F-Secure Corporation
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