44CON 2019

Almost everything about us – our handwriting, DNA, faces, voices, fingerprints, even our eyes – can be used to distinguish us from the seven billion other people on the planet. These physical identifiers can allow law enforcement to trace back real-world crimes to offenders, and enable biometric authentication mechanisms. However, such identifiers are often irrelevant when it comes to attempting to track or disrupt threat actors.

In this talk, I will discuss, explore, and explain identifiers which are unintentional, non-physical, and generated as a result of human behaviours and activities, but which can still be used to uniquely identify and/or track individual users in the digital realm. I call these identifiers “human side-channels”, and will explore how they work; how they can be used for both attack and defence; and how they can be countered.

I’ll examine three human side-channels in particular: forensic linguistics; behavioural signatures; and cultural references. I will start by exploring the theories underpinning these side-channels, which are rooted in personality psychology and the concepts of consistency and distinctiveness as a result of our unique experiences, training, and feedback. I’ll then explore how they work; walk through case studies and examples/demos of using them practically in security contexts; and discuss how they could be practically applied to investigate and track threat actors, in situations ranging from hostile social media profiles to post-compromise exfiltration and privilege escalation.

I’ll also examine the privacy implications of each technique, and how such characteristics – which are much harder to recognise, obfuscate, or spoof – could be used to erode privacy. I’ll go into detail regarding possible countermeasures to disguise your own human side-channels, and I’ll wrap up by outlining some ideas for future research in these areas.