Validate that an unprivileged user has the correct access

Question

I created a simple unprivileged user on my Ubuntu system which will be used to run my network applications (Firefox, etc..) from a limited user.

My purpose is to lower the possible damage that can be caused to my data in case of a malicious site trying to exploit a vulnerability in one of these network applications.

Is there a simple way to check that this limited user really limited as I expect it to be?

For example, I ran find / -perm -o=w to see if there are important files that this user has permission to change.

Answer 1

There's no magic bullet. You could hire a professional to do a security audit, and even then you wouldn't be completely sure.

Your best bet is to log in as this user (or execute commands under su limiteduser), and try poking where you shouldn't. For example su limiteduser -c 'find / -writable' will report all the files the user can write to.