Stop Sending Me a Virus!
Everyday when you read your email, some 'so and so' has sent you a virus. After awhile this is getting pretty old and you want it to stop. So you just dash off an email to the sender and tell them in no uncertain terms to stop sending those nasty things to you and clean up their computers!
Problem is, the person you sent that to isn't the one that sent it!
Well then, who did send it? Good question! The worms and viruses out there today all pretty much have 'email spoofing' in common.
Email spoofing fools just about everyone the first time you get one of these emails. The virus (or worm) on an infected computer steals the email addresses from the victim's address book and then sends an infected email to everyone in the address book using one of the addresses as the sender's address.
This practice is very confusing to lots of folks. Look at this site to find out about email spoofing. Cert®.org
The only thing you can do is keep your anti-virus software updated and keep deleting those emails with attachments! Also delete SPAM messages without reading them. (You also need to keep Windows updated with the latest security patches.)
Sometimes we can determine who sent an email by reading the 'Headers'. With email spoofing, I don't know! Read what Wikipedia has to say about it!
Some sites to help you learn about email headers.
Another informative page about email spoofing is on Ask Leo.