Detecting intruders

[Balanga]

Is there any way to detect intruders and find out what they have been up to?

I see a lot of failed passwords and invalid users when looking at my system logs.

I'm not sure how to tell what is visible from the outside world.

[heper]

uhm?

by default pfSense doesn't allow logins from the wan side… you shouldn't allow it either.

[KOM]

I'm not sure how to tell what is visible from the outside world.

Look at your firewall rules on the WAN tab.  That's what is visible to the outside world.