Bitdefender Antispam Lab researchers have been analyzing a wave of extortion messages sent via backscatter spam or “non-delivery report messages” (NDR). Beginning Jan. 4, spammers have been focusing on delivering tens of thousands of messages to recipients in Eastern Europe, including Romania, Hungary and Croatia.
Backscatter spam attacks are the result of malicious actors forging or spoofing the “From” address (using valid e-mail addresses) in a sent email. Once the spam email is assembled, the spammers send the messages to non-existent recipients, tricking the email servers into returning the undeliverable message to the forged e-mail address in the “From” section of the email header.
Backscattering is used to bypass spam filters and get recipients to read a message or access attachments. Most often, an NDR recipient will check the validity of the message before deleting it. The non-delivery report messages generated as a result of this spam campaign contain extortion messages claiming recipients’ devices are infected with malicious software.
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