Two step verification.
For example if I want to sign into Strava on the main PC it sends an email to my Sky email account with a verification code. To read that email I have to sign in to Sky - which sends a verification code by text message to my phone.
It can be a pain but if it helps prevent fraud then I'm all for it. Obviously if someone got into my Strava account so what. If they got into my banking then it's a bit different.