can you recommend any (opensource or trusted) android apps to check who’s using your wifi? or any cmd prompt code to search on the desktop?
a small doubt: can anyone hack your computer through WiFi? If so, How to prevent that (or) How to take measures after you think you been hacked?
https://shop.hak5.org/products/lan-turtle
Assume physical access, someone walks in and has 5 minutes out of sight. A decent wpa2 password would take an extraordinary long time to brute force. Something like above gets deployed and allows remote access in seconds on an unprotected lan. As noted in another comment sketchy IOT gear is a threat people install willingly. The old test of leaving a loaded USB in the parking lot catches more people than is reasonable. Don’t assume a physical door is going to stop someone more than a proper technical barrier.