Terrorists made their emails look like spam to avoid detection

Terrorists once used spam email subject lines to avoid being detected by security services, the former deputy director of America's National Security Agency has revealed.

In a paper [published in the American Mathematical Society and flagged up by Quartz, Michael Wertheimer writes that the security services' algorithms filtered 'spam' out of the messages being monitored - a loophole which terrorists had used to avoid detection.

He details how shortly after the 9/11 attacks they found an email on a laptop left in Afghanistan by Taliban fighters with an email subject line reading "CONSOLIDATE YOUR DEBT".

It is surely the case that the sender and receiver attempted to avoid allied collection of this operational message by triggering presumed “spam” filters. Indeed, this is exactly how intelligence and counter intelligence work: an escalating series of moves to discover and avoid discovery of information.

• Michael Wertheimer

The NSA was obviously aware of the trick, and Wertheimer says they are constantly changing their algorithms, which means it is likely that nowadays spam email is the domain of bad marketeers rather than jihadists.

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