My trusty laptop which has been running Knoppix 3.4 for over a year now has suddenly lost speed and I am not sure whether it is a problem with the hard disk (which seems to be making some noises) or whether I have caught a 'worm'.

I go on the internet a lot (ADSL) but always through a firewall and there doesn't seem to be any extra network traffic not initiated by me (i.e. spyware). The hard disk seems to thrash a lot (quite extreme) when the system is starting and when programs are loading but once the programs are in memory the disk calms down.

This makes me think that I have a disk problem (and need to get a new one) but can anyone tell me how I check for these things in a more thorough/systematic way?

What is the best tool for scanning a disk for errors/problems? And are there Worm/Spyware dangers for Linux? Maybe you can point me to any web sites which explain these issues?

Any tips would be very gratefully received.

Many thanks,
Alan Searle.