Wireless-only phone users have become a one-stop shop for scam callers

It's the dark side of wireless life. As more people abandon their land lines and go wireless-only, thus becoming much easier to reach, scammers have grown increasingly brazen in dialing for dollars.

A survey released this month by the mobile communications firm Truecaller found that three-quarters of U.S. scam calls now are received on wireless devices. That's a big jump from last year, when half of all such calls still came in on land lines.

Some other findings:

About 27 million Americans reported losing money to phone scams over the last 12 months, up 53 percent from a year earlier. Total losses were estimated at $7.4 billion, or an average of $274 per victim.

"The scammers go where the targets are," said Tom Hsieh, a Truecaller vice president. "As people move away from land lines, so do scammers."

It's not hard for bad guys to find you. Your phone number might be posted online, available from public records or in a hacked database.

Last year, health insurance giant Anthem reported that as many as 80 million members had their names, phone numbers and other personal information accessed by hackers. Similarly massive security breaches have been announced in recent years by Target, eBay and others.

Aside from purchasing hacked numbers on the black market, Manship said, scammers also obtain people's contact information from old handsets that were never completely wiped clean.

Once scammers put together a call list, they use automatic dialing machines to go after potential victims. When a call is answered, the scammer gets on the line.

An especially popular racket last year was the IRS scam, which involved a call supposedly from the tax agency and a threat of arrest if overdue taxes weren't paid.

The IRS said last week that such calls are now the most common tax scam. Since 2013, it said, at least 5,000 victims have been bilked out of more than $26 million.

Experts say you should immediately hang up if you receive a call announcing that you've won a prize or are due some money, or if you're pressured to make an immediate decision.

Ask for the caller's name, phone number and location. Tell them you'll call back. Needless to say, if they won't provide this information, the conversation is over.

If they do give a number, Google it and see what comes up. If it's not the actual agency or company, walk away.

Mike Davis, a researcher at Seattle consulting firm IOActive, said you're only increasing your chances of being targeted by scammers any time you dole out personal information online. Internet surveys that promise free gifts or sweepstakes winnings are especially troublesome, he said.

So just remember: Your grandchild isn't rotting away in some overseas jail. Microsoft isn't calling to fix your computer. And the IRS never, ever calls taxpayers on the phone.

But do pay attention if the agency sends you a letter.