Welcome to the Virus Encyclopedia of Panda Security.
Happy is a worm that arrives in an e-mail message with the subject Happy New Year 1999!! and the following attachment: HAPPY99.EXE.
The text included in the message entices users to open the attachment, by trying to convince them it is just a greeting card.
Happy is not considered dangerous, as its only objective is to spread to other computers without causing any destructive effects.
It is capable of spreading at great speed, as all the actions it carries out at aimed at propagating to other computers by e-mail.
A clear indication that you have received Happy is an e-mail message with the following characteristics:
Upon running the attachment a window is displayed, which seems to simulate a fireworks display to celebrate the New Year: