UNDATED - Despite repeated alerts, tens of thousands of Americans may still lose their Internet service Monday unless they do a quick check of their computers for malware that could have taken over their machines more than a year ago.

The F.B.I. says about 64,000 computers in the U.S. may get knocked off the internet on Monday.  That's because last fall F.B.I. agents discovered - then took offline - the computer servers that criminals were using to control PCs carrying this malware.  The agency then set-up replacement servers so the victims would not lose internet access immediately.

The way the scam worked, attackers steered victims to web pages carrying online ads, advertisers then paid the attackers for each click to a page carrying their ads.  The click fraud scam netted at least $14 million.

You can visit an F.B.I. approved website where you will find links to services that will run a quick check on your PC.