Can anyone tell me why this happens? When I am on-line I see my dsl modem activity light flash a few times and then my hard drive starts reading and writing. It does this only when I am on-line, I turn off my router and the activity stops. netstat indicates no listening ports. I am using Suse 10.0 behind a router to a dsl connection. Running the standard Suse firewall with default setting. I believe I have all services turned off that I don't need. No servers needed or running. I just use my box for e-mail and web surfing.

How do I check out whats going on?
Am I too paranoid?

Thanks for your help and ideas.

You could try to sniff the traffic with Ethereal while you are online.

Then you should see where the packets come from / where they go.

I guess it is only doing broadcasts, discovery messages, etc.
But the hdd activity confuses me

Do you have a fixed IP?
Maybe you are getting old packets of P2P users.
Then your firewall logs the packets which could explain the disk usage.
It could be a process trying to update something.

What you could do in this case is install Ethereal.
Launch Ethereal, launch your connection, don't do anything, don't breathe and stop it after you have something.
Right click on one packet and choose "follow tcp stream" , you should see the text being sent/received.

Have you tried just running top, or ktop or whatever gnome's version of it is and seeing what processes are using the CPU?

Use ps aux to see all processes.
Use lsof to see all open files in your system. Usually a lot of libs will appear.