While infecting a computer, the worm creates files in the Windows system folder with 'SKA' in the filename or extension. The worm later sends a copy of itself as an attachment to others when users of the infected system send e-mail or posts messages to a newsgroup. Attachments are named Happy99.exe or Happy00.exe PrettyPark. Worm Similar to the Happy99 worm, but circulates as an e-mail attachment named PrettyPark.exe. When the attached program is executed it may display the '3D pipe' screen saver.
Viruses also infect the system areas of the disk.
In most cases that's where human beings come in. We send e-mail document attachments, trade programs by exchanging diskettes, or copy files to servers. When the next unsuspecting user receives the infected file or disk, the virus is spread to their computer, and that's how the virus spreads. Worms on the other hand don't rely on humans to spread. This means a computer worm spreads much more rapidly than a virus.