6. Do not open attachments in emails, even from friends. Certain viruses can access someone's address book and copy the email addresses found there. Then they can send you email that looks exactly like it came from your Aunt Tilly using a technique called address spoofing. If you need someone to email you an attachment, make sure they tell you about it first or request it from them in advance.
For more security information visit Seniors Guide to Computers.