Im running Mandriva 2007 as a home PC and im reasonably new to Linux, 3months etc. PC is Not mission critical. I am running the mandriva firewall and firestarter front end.

Out of the blue the otherday I was hit by unusual PC behaviour. Opened Mozilla and tried to go to google. Got immediately directed to a porn site and this was followed by a trashy pop up.

Shutdown browser and reopened. Tried to go to google and got a suspect google page saying they were refusing connection because I was appearing as a type of virus? It looked like a possible spoof webpage. Stupidly I never noted the address (too early in the morning). However try as I might I could not get past this page to google.

When I tried to shutdown my machine there was alot of hardrive activity that held up the logoff and shutdown.

Following day I fired up PC and firestarter GUI but my problems were gone.

Any ideas? Anything I could look for or check?

There are virus scanners for Linux, have a look at ClamAV.

If you are on a wireless network it coul have been a man in the middle attack.

Sounds like DNS cache poisoning to me.
http://en.wikipedia.org/wiki/DNS_cache_poisoning

On a Windows box I'd tell you to run:
Not sure what the equivalent command is in Linux however. Maybe someone here can enlighten us both.