I ususally let them talk for a while while going to make a drink/dinner/load the dishwasher/unload the washing machine/any other chore that needs doing... Then I go pick up the handset again, and inform them that I work in IT, have anti-virus softawre, own a router with a firewall, and make sure everything is scanned/patched on a regular cycle and tell them they can take their suggestion, fold it until it is all corners and stick it where the sun doesn't shine. Usually works
I like to attempt to change the subject dramatically. I was once talking for 10 good minutes about the new harry potter (not this one, the last one) He was constantly trying to get it back to computers. It was hard work
I got a bit tired of PTV trying to sell me their World subscriptions because I'd had to register on every forum I used on the old OWSs (you could post on any with one account but you couldn't start threads) and I'd come up for every one of them. In the end I went into all my profile settings and changed my registered name to be one of PTV's directors (different one each time) with my address at their head office, and the phone number being the number for the main switchboard.
