Cover your tracks in Bash

unset HISTFILE

Bash shell stores history of the commands you execute, and you can inspect this history using the history command.

But if you do not want your session history to be saved (maybe you are doing something nasty, which you don't want others to know about), you can use the above command to disable the history logging feature for your session, and nobody will know what you did.

PS: There are other audit trails which can still incriminate you, so don't smugly assume that the above command makes you an invisible hacker.