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