backscatter spam

(redirected from reverse NDR)

backscatter spam

A spam method that relies on mail servers returning messages to the sender. The spammer forges a valid e-mail address in the "From" field of the spam message and makes the "To" address a phony e-mail recipient, but to a real company. Since there is no e-mail account with the phony name, the receiving company's mail server bounces back the message before sending it to the spam filter. As a result, the spam winds up in the inbox of the intended recipient as undelivered mail. Also called "bounce spam" and "reverse non-delivery report spam" (reverse NDR spam). See NDR spam.
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Several IP-specific reports also show sources of Reverse NDR attacks, prohibited attachments, and spam originating from blacklisted mail servers.
Not only does Reverse NDR eat up huge amounts of mail server resources, but also the enterprise's domain risks being blacklisted by ISPs, customers, and organizations with which the enterprise does business.
In addition to improving enterprise productivity and limiting objectionable or unwanted email, Praetor can stop invasion from spammers who use Reverse NDR attacks.