You open up your email program to find 100 or more messages downloading. Turns out, most of them are undeliverable bounce-backs.  The problem?  You never sent these messages in the first place!  So is your computer infected with some new, malicious virus?  Maybe it's been struck with a voodoo curse?

Most likely, none of the above.

This rather annoying trend is an effective spamming technique called "backscatter".   Backscatter has been around for a few years, but is finding renewed popularity from the bad guys in the spam wars.

This clever trick has recently gained momentum amongst the unsolicited commercial email (UCE) marketers as a means to circumvent spam filters in the ongoing cat-and-mouse spam/anti-spam wars.

The gist of backscatter is this:  a spammer sends out hundreds of thousands of their messages, spoofing the sender email address.  They obtain your email address by either randomly generating it (i.e. their software guesses and plugs in email aliases), or by scouring your website to pick up legitimate email addresses.

Spammers know that anti-spam filters, such as the MailScanner software Hurtdidit uses, are becoming increasingly effective at blocking their efforts.  On a typical day, MailScanner filters out over 20,000 spam messages before it has a chance to reach our clients' inboxes.

However, anti-spam filters will rank undeliverable messages as "less likely" to be spam, particularly if it appears that the original message was coming from a legitimate email address--your own.

To bypass the threat that anti-spam filters pose against their unscrupulous practices, UCE marketers have began using this built-in trust as a loophole, to get their messages through. 

So how can we combat this annoyance?  Well, unfortunately not much can be done.  Until a new method is devised amongst the anti-spam software developers, the best advice I can give is the same policy you should always have when it comes to spam:  ignore it.  Never open or click on any links in a UCE message, and never, ever click any supposed "unsubscribe" links in a spam email, as this merely serves to confirm your email as an active account.

Aside from backscatter temporarily filling your inbox with annoying junk, it is generally harmless to you as an end-user, and should simply be ignored.