Longlining: the new phishing attack targeting businesses

Targeted spear-phishing and traditional mail-bombing attacks are merging to create yet another new genre in the email scam game – longlining.

This name isn’t simply another fishing pun, but rather a literal description of how this technique works.

Longline fishing is a commercial practice that employs a single line several miles long, baited with thousands of individual hooks. Longline phishing gets around traditional security systems by a process of “mass customisation”, employing a rapid bombardment of thousands of uniquely targeted messages.

Many security gateway filters will be looking for identical or similar messages from a single source, so they won’t detect a longline attack, the messages of which have widely differing subject lines, content and, most importantly, originating IP addresses.

This multiple-hook analogy applies to the body content of the messages themselves, which will contain multiple variations of the embedded malware target URL, the ultimate destination of which will almost always be a trusted site that’s been compromised in some way (which helps evade reputational filtering on the URL).

Think of longlining as a parallel phishing delivery system and you’re in the right ballpark.

Armed with the capability to send hundreds of thousands of these malicious URL hooks in a matter of hours, plus the ability to bypass many corporate gateway filtering systems, the bad guys increase their chance of exploiting a zero-day vulnerability before the IT department has been able to patch it.

I’ve heard longlining described as “combining the effectiveness of spear-phishing with the speed and scale of a virus attack” – and that scares me, even if it doesn’t scare you.

It would certainly encourage me to make sure my IT security education programme was up to date.