I've replaced reconnaissance commands (a handful of them found here: https://www.cybrary.it/blog/linux-commands-used-attackers) -- whoami, uname, id, uptime, last, etc

With shell scripts which run the command but also send me a notification via pushover. I'm running several internet-facing services, and the moment those get run because someone is doing some sleuthing inside the machine, I get notified.

It doesn't stop people getting in, I've set up other things for that -- but on the off chance that there is some zero-day that I don't know about yet, or they've traversed the network laterally somehow, the moment they run one of those commands, I know to kill-switch the entire thing.

The thing is, security is an on-going process. Leave any computer attached to the internet long enough and it'll be gotten into. I don't trust being able to know every method that can be used, so I use this as a backup.