I keep a referees whistle close to the phone and when contacted by one of the scammers (usually named Paul or John, but with a suspiciously Indian accent) informing me that my computer is sending them alarms I keep them on the line asking them to listen carefully to the strange noise it's making.....then let them have it. 
Been so successful I usually receive a return phone call within 20 seconds with a tirade of abuse (didn't know Indians knew so many swear words) when I laugh and hang up. So successful in fact the last two continued to call me for 45 minutes after the original call. When tired of the game I let it go through to voice mail, which is when they quit as they don't want a recording of what they are saying being able to be played back. Keeps them from scamming someone else meanwhile......and no more calls for the last month whereas I was receiving 2-3 every week prior.
Been so successful I usually receive a return phone call within 20 seconds with a tirade of abuse (didn't know Indians knew so many swear words) when I laugh and hang up. So successful in fact the last two continued to call me for 45 minutes after the original call. When tired of the game I let it go through to voice mail, which is when they quit as they don't want a recording of what they are saying being able to be played back. Keeps them from scamming someone else meanwhile......and no more calls for the last month whereas I was receiving 2-3 every week prior.
At the summit of the picturesque fens