NDR or Backscatter Spam - How Non Delivery Reports Become a Nuisance

You might remember a while ago we mentioned MP3 spam, which in October last year was the latest evolution in spam.

Currently there is a new type annoying mail-server owners the world over, it’s known as NDR or Backscatter Spam and involved NDRs or Non Delivery Reports (those emails you get when you send a mail to a non-working or no longer active account).

Research shows that up to 90% of emails received by companies are spam, and spammers have adopted a variety of methods to bypass spam filters used in anti-spam software. In the beginning, spam was mainly text based but over the past few years, spammers have resorted to using embedded images and attaching common file types such as mp3s and Excel documents in emails to gain access to mailboxes. Another option is NDR or non-delivery report spam.

NDRs are a common part of email exchanges. Users receive NDRs, for example, when an email does not arrive at a recipient’s address and notification is sent to the sender. However, spammers can cause a considerable increase in NDR activity because they send junk mail to thousands of email addresses. Some are genuine but others are not and these are used to generate NDR messages by manipulating the ‘From’ address to use a real domain sender. This results in email users receiving NDRs from people they had never sent an email to in the first place.

This white paper explains what NDR spam is and how administrators can take effective measures to reduce the impact on their email servers.

To download a copy of the white paper, please visit:
http://www.gfi.com/whitepapers/ndr-spam.pdf [PDF]