Malevolent mailers are increasingly hitting systems with email flooding attacks never designed to appear in inboxes.
Darkmail, speculatively targeted, unsolicited mail, has risen 400 percent in the last twelve months according to a report from email filtering company Email Systems.
"Spam attackers are becoming increasingly speculative in their approach to reaching an actual user, with the overall volume of unsolicited mails having increased significantly and, more worryingly, the amount that's mis-targeted having increased by a different order of magnitude altogether," said Neil Hammerton, CEO at Email Systems. "Unfortunately this is resulting in a great deal more unnecessary email traffic which has the potential to severely affect unprotected corporate networks."
Darkmail is primarily used in distributed denial of service (DDoS) attacks and directory harvest attacks (DHA) in which a specific domain is hit with a flood of emails through an alphabetical list of names.
But over the last year darkmail is being used to brute-force spam through filters and is clogging up bandwidth.
Email Systems said that in one recent example a manufacturing company with less than ten employees was hit with more than ten million emails a day, each sent to a different email address within their domain – according to the filtering firm such attacks are now commonplace.
Earlier this month SC reported some spammers are turning their back on the spam business. Self-styled spam king Scott Richter has now been spam-free for over six months.