My Mandriva internet connection program just Said that Someone tried to port scanning attack on my connection.

Attacker: 3.234.106.266 service: 1029 network interface: eth0 protocol: udp

What in the world is this, and how do I protect my linux system??

Generally, to protect yourself, you want to install and use a firewall. The preferred method is to have a hardware firewall (like a Linksys router or an old linux box running IPcop or similar) and then use a software firewall on your machine. This way your machine isn't actually seen by the outside, the hardware firewall is.

Anyway, in short, use Guarddog for KDE desktop or Firestarter for Gnome (those are the defaults usually). Personally, I like fwbuilder.

If you're interested to see if your machine has open ports, try going to https://www.grc.com/ or http://www.auditmypc.com/ to test your firewall (or lack thereof).

I don't use Linux as much as I use windows but I'm willing to try to help you out. I need a bit of information before we get started on solving this problem. What version are you using and what security software are you running?