As well as avoiding excessive body piercings and not wearing a hoodie, pen testers can be even more inconspicuous by pretending to use Windows…:
[…] The Kali undercover feature meanwhile is designed to give Kali Linux users a way to remain inconspicuous when doing security assessments in public, he notes. “The classic Kali dragon is so iconic it’s often a dead giveaway for what you are doing, even for people that don’t work in this space,” O’Gorman notes. The undercover theme is designed to appear like a Windows desktop to the casual viewer. The theme is unlikely to hold up to a detailed examination but is perfectly adequate for fooling a casual observer, he says.