Symantec’s Monthly State of Spam report for March showed an increase in bounced messages that found spammers forging sent email addresses and using them in the “From” header of their own Spam messages.

Reminiscent of Backscatter, spammers are taking advantage of mail transfer agents configured to send back a list of failed email recipient addresses, an explanation of the cause of failure, and a copy of the original email. This opens a window for Spam attacks, as anti-spam filters do not block most “failed email” replies. Since spammers forge the sender’s address, this mail is going to be received by people who have nothing to do with the Spam.

Corporate networks will feel the greatest burden of the increased attacks. Using increased bandwidth and an increase of unwanted Spam messages in users’ inboxes will result in lost productivity. Networks are encouraged to configure mail transfer agents to not send back a copy of the original failed messages and require signatures for outgoing emails.

Tags: Backscatter, Emerging Threats, Information Security, Spam

Author: Christopher