There's something easier than writing a program to make computers mess themselves up. It's writing a letter to make humans mess computers up.
Virus hoaxes are just that - hoaxes. They're letters which pretend to be a virus alert, or some other sort of computer security alert, and which aren't. They're worded to frighten people and get them to forward the message to 'everyone they know' - or at least to a lot of other people.
This forwarded email can slow down or even stop a mail server, fill peoples' mailboxes, and, of course, frighten them and cause them to lose time and waste time and energy on something which is just a hoax.
You can't really defend yourself against receiving virus hoaxes except by educating everyone you know. But you can avoid sending hoaxes on. In a corporate environment, just forward the virus alert to the IT department. It's their job to know which ones are hoaxes and which are real.
If you're not in a corporate environment, and you feel you must pass on a virus alert, don't just forward the one you received. Write your own.
First, check with a list of virus hoaxes. Links to several of them are at the bottom of this article. If the forwarded email is a hoax, send the URL of the hoax page to the person you forwarded the mail to you, with a gentle note saying 'hey, you were hoaxed'.
If it's not a hoax, your mail should include:
The URL of a reputable site which contains verified information about the virus - the actual URL of their page for that virus is best. Links to virus information sites are at the end of this article. You can probably find this information at the same place where you checked whether the message was a hoax.
The date you send the message, and a guess at an expiry date (a 'don't pass this on after date ' date). Make the expiry date no more than a month after the date you send it - if it's dangerous, it'll be all over the papers anyway. And after a month or so, most peoples' virus-check software will have that virus in the database.
Why you think it's worth passing it on to the people you're sending it to.
Don't write a sensational letter. Just write something calm and helpful. People in this culture have learned to ignore sensationalism anyway.