Backdoor A backdoor is a hidden way in. Once placed or opened, it lets the attacker return to the machine — with no password, no authorization and no entry in the ordinary records. A backdoor can be opened by malware while it runs, but it can equally be a user account nobody watches, or web shell access left on a server.

Remote access trojan - RAT A RAT gives the attacker remote control of your machine. Once inside they can browse files, switch on the camera and microphone, record what you type and run commands — all of it live, as if sitting in front of your screen. It resembles remote support tools, only on the wrong side of the law.