I don’t want to come off as an *** but this is not the work of a “hacker”. You sound like my grandmother.
“try to minimize the amount of time your online”
This is the most absurd thing I’ve ever read in this forum.
No hacker will sit down and try to track down a random person like you and put in the effort to “hack” you just to mess up a few blueprints in UE.
You have nothing to worry about.
“Hacking” someone isn’t just searching for your username and connecting. It would be really hard to access your computer unless you did something like posting very specific information online.
Either someone in your house accessed your computer.
Or you have a wifi without password that someone close to your network just logged onto.
Or you use some remote desktop software and somehow posted connection information.
Or the files just became corrupt by some other reason. Which isn’t uncommon when working with this kind of stuff.
All those explanations are far more likely than some random person “hacking” your computer.
Furthermore, make backups on separate drives, or even better on some cloud server.