GFI Software, a leading developer of network security, content security and messaging software, has launched a paper to explain what NDR spam is all about and why spammers have resorted to this effective method to distribute unsolicited mail.

Research shows that up to 90 per cent 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 an 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 to whom they had never sent an email in the first place.

Unless action is taken, email servers could be inundated with useless emails thereby hogging system resources and affecting performance. The best way to stop NDR spam is to deploy anti-spam software that can identify spam in NDRs and delete them from the server.

A variety of technologies are used and anti-spam software like GFI MailEssentials, the number one anti-spam filter on the market, uses Bayesian Filter, DNS Blacklists, Spam URI RealTime Blocklists and Keyword Checking to keep NDR spam at bay. GFI MailEssentials also uses a Directory Harvesting feature on the email gateway to drop email messages and NDRs sent to non-existent users.

This paper explains what NDR spam is and how administrators can take effective measures to reduce the impact on their email servers. A copy of the paper can be downloaded from www.gfi.com/whitepapers/ndr-spam.pdf