Linux permissions look intimidating. They're just math.

4 = read 2 = write 1 = execute

Add them up:

7 = full access

6 = read + write

5 = read + execute

4 = read only

Three digits = three audiences (owner, group, everyone).

"chmod 777" means the entire world can read, write, and execute that file.

That's how privilege escalation starts.