This is my personal Top 8 of worst suggestions I’ve read, took or gave to other Linux users so far, feel free to add your as comment.
Legend: Q: Question, BA: The bad answer, GA : What could have been a good answer
1) Q: I have a file i can’t read/write/execute with the user i want!
Bad: “chmod 666 file” – This makes the file editable and destroyable by anyone.
Worse: “chmod 777 file” – This makes the file editable by anyone AND sets execute permissions for anyone. This means that any user can edit the file to do something malicious for the next user to (accidentally?) execute it.
Worst: “chmod 7777 file” – Also gives setuid and setgid permission. With this you’ve just given any user permission to fubar your machine, especially if the file is owned by root.
GA: Check which user and group have permission to do the operations you need on that file, subscribe the user to that group and/or change the owner or the group of that file.