Worms
A worm is a small independent program (often an email attachment) that
moves over networks (LANs or the internet) from computer to computer. It's main
purpose is to distribute copies of itself, usually by automatically sending
emails containing the worm to other people. Worms themselves don't infect other
programs, but they may contain trojan horse or viruses, which may do it.
History
- Morris worm (internet worm), an experimental worm used by Robert T. Morris
in 1988. He didn't expect the huuge "success": Within hours, thousands
of computers were infected
- "Melissa" (1999), contained a macro virus, infected 100 000 computers
within 3 days.
- "Loveletter" (2000) infected millions of computers within one
day.
- "Nimda" (September 2001) used an exploit in Outlook (allowing
attached exe files to open without doubleclicking it) and IIS servers (the
infected server would send, when visited, eml-files containing the worm. When
activated, Nimda opened the C-drive for use through the network, and opened
a guest account with administartor rights.
How worms work:
- They may be sent as email attachment. Doubleclicking the attached worm will
start it and infect your computer.
- Some use exploits.
- Worms usually change the registry, they change the autorun file.
- Some newer worms even try to deactivate virus scanners or firewalls.
- Some worms also contain trojan horses.
What to do against them:
Don't click on unknown attachments. They may be worms.
Full page view