security

ok, so i know this is technically sensible as accounts do get hacked, but i kind of wonder how they go about assessing that this is happening.  

i was a bit confused when i signed in to write a post yesterday and despite signing in no problem, from a regular location, i was then asked to verify who i was. what? why? maybe i would have understood if the sign in had been from a weird place in the world or something but it came from the place where i usually sign in to write posts. i tried several times, thinking it was maybe just a one off, but no, it just kept telling me to verify who i was. i was eventually able to enter my account this morning, thankfully.

interestingly, when my account was hacked a few weeks ago, i got zero information about it from the system but emails from people asking me why i'd sent them a random link to some random stuff. so i'm left wondering: how exactly do they assess a possible threat?