E-mail Address Spoofing; Strange yet familiar mails

A common pattern in the way Worms and one tactic Spammers employ is that they send mails which have spoofed from address. This means that the from address you see in the mail is not actually the address from which the mail originated.
Worm when it infects a PC, makes a list of all e-mail addresses found in the infected machines address book, html pages, or any other file is searched and a list is made by the worm. Then it chooses one ‘from’ address and another address as the ‘to’. The person whom it supposedly come from, may not know about the mail at all.

Spammers follow similar procedure so that the source of the spam is hidden, bounced back message goes to spoofed addressee, and spoofing also allows spammers to avoid negative publicity.

Strange Bounced Mail; when the mail is sent to someone fraudulently with your from address and if for some reason that mail could not go through, it gets bounced back to you. This is how you get undeliverable message for mails which you haven’t sent. Mail may be getting returned due to over quota or because server detected virus in the mail.

Affect of spoofing by Virus/Worm: a worm triggered and spoofed mail wont be sending you cakes. Most often they come with a mail which carries the worm code itself to start work in your PC. If your network or your PC does not have effective antivirus in place, you are sure to get infected and start infecting others.

How to Investigate and find out: currently there is not much you can do to prevent address spoofing excepting the normal spam filtering. Your address can be inserted by someone as their from address very easily in their e-mail program. In future, the senders domain name may be verified automatically by the e-mail server trafficking the mail to ensure that the sender actually is the sender it claims. This technology is in the process of being perfected and may offer a solution.