VBS/Happytime is a VBS worm that propagates in two different ways - as a slow worm similar to JS/Kak, and as a fast worm - mass mailer.
Depending on the settings of your F-Secure security product, it will either automatically delete, quarantine or rename the suspect file, or ask you for a desired action.
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More information on the scanning and removal options available in your F-Secure product can be found in the Help Center.
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Happytime first drops following files that contain the virus code:
help.hta help.htm help.vbs
Then it executes its payload, that activates if the sum of the day and the month is 13. At this time it deletes all files with extension ".dll" or ".exe".
Happytime.A uses a counter, and when it reaches number 366, then the worm sends itself replying to all messages listed in Outlook Inbox with a following message:
Subject: Help Attachment: Untitled.htm
where "Untitled.htm" is another file where the virus saves its code.
Next the worm replaces the current wallpaper with "Help.htm" via registry.
Happytime.A then prepares the system to send itself as a slow worm using Outlook Express 5.0. To do this, it creates a stationary that contains the worm code.
Finally the worm infects all files with ".htt" extension in the "\WEB" directory located in the Windows installation directory. Therefore the worm is executed each time when a folder viewed as a web page.
On the top of its code, the worm contains the following commented line:
I am sorry! happy time
Technical Details: Katrin Tocheva and Sami Rautiainen, F-Secure; May 2001