Recently, both myself and a lot of users at work here have received a barrage of “undeliverable” email messages. I’m not talking about a few here, but hundreds a week.

Naturally, the first thing I thought is our mail server has been compromised. Long story short, that was not the case. Next, I thought it was our client machines which have been hijacked… again, not the case. It turns out we are just victims of “backscatter” spam.

The article linked above (ironically, I saw this the day after the problem started) explains what backscatter spam is, what causes it and how to handle it. This is an informative read for those of you are concerned with all the undeliverable email messages you have been getting.