As the oldest of the baby boomers turn 60 this year and seek out secure investments for their retirement money, some scam artists are smelling blood.

They prey on seniors' financial fears, violate their trust and threaten their nest eggs. Lots of them pitch what they call high-return, low-risk investments. But in many cases, the products — annuities, oil and gas investments and promissory notes, among others — are inappropriate for seniors, if they exist at all. Regulators say these scams are increasing as the retiree population swells.

Henrietta Tolhurst, 89, was bilked of $6,800 this year when a scamster phoned her and told her she had won a $2 million prize. All Tolhurst had to do to claim it, she was told, was pay the "legal fees" on the prize.

She handed over the money but got zilch in return.

"It sounded so believable" at the time, says Tolhurst, who lives in Santa Monica, Calif. "Honestly, it didn't occur to me that I was being scammed."

Unregistered securities and annuities — insurance products that let you trade in a lump sum for a lifetime stream of income — are the most common financial products involved in senior investment scams, according to the North American Securities Administrators Association (NASAA).

The products and pitches, though, are constantly evolving.

"What I find most frightening is the level of sophistication that these scam artists will use in targeting seniors, the array of tools they use to lure them into investment fraud," says Mary Schapiro, the incoming CEO of NASD, a self-regulatory body for the investment industry.

Why are seniors tempting targets? "That's where the money is, and that's where the fraud is," Christopher Cox, chairman of the Securities and Exchange Commission, told USA TODAY.

The 79 million baby boomers have more than $8.5 trillion in investable assets.

Today, nearly half of all investor complaints, and about a third of enforcement actions, involve investors 50 and older, according to the administrators association, or NASAA.

Here are some ways that scamsters target seniors:

•Free-lunch seminars. These events, held in hotels, country clubs and community centers, are booming. They may seem innocuous enough: You get an invitation in the mail or see a newspaper ad about a free financial seminar. There, an "expert" will offer you tips on how to protect your assets in retirement.

Free meals and social contact lure seniors to these gatherings. The problem is that once you're there, the salesperson will ask for your contact information and sometimes for details about your financial assets.

"Before you go in the salad-bar line, you have to fill out the form," says Patricia Struck, president of the NASAA.

The organizers usually follow up the seminars with high-sales-pressure visits to seniors' homes. They often try to persuade you to buy a high-cost, high-commission annuity, so you don't outlive your assets. Or a living trust so the state won't divvy up your assets when you die.

Annuities and living trusts are legitimate products — but not when they're pitched as a one-size-fits-all solution, as can be the case at these seminars, regulators say.

As more of these free-lunch meetings crop up, the NASD, the SEC and state regulators say they are stepping up their scrutiny. Regulators are looking into "the sales literature, the promotions that are being used" at these events, Cox says.

Thursday, the SEC filed an emergency action in a U.S. district court to halt an alleged securities fraud targeting retirement investors through free dinner seminars. The SEC's complaint says the promoter diverted to his personal use some of the more than $22 million that he raised by promising to invest the money in real estate.

•Church and community group fraud. Con artists often belong to the same social group, church or gardening club that you do. And they won't hesitate to use that connection to their advantage.

They try to gain seniors' trust by explaining that they share the same background and interests — so why not invest money together?

Seniors are particularly vulnerable to these scams, Struck points out, because they have more time to join different organizations, and many tend to be trusting.

The financial blow of this misplaced trust can be devastating. In California this year, securities regulators issued a "desist-and-refrain" order to a Korean-American man, claiming he had defrauded 19 Korean-Americans of $2.5 million.

The state says the man promised to put clients' money in stocks and bonds yielding 4% to 6% monthly. If clients asked to withdraw some funds, he would use new investors' money to pay old investors in a so-called Ponzi scheme, the state alleges. The case continues to be investigated.

•Fake contests. These scams usually involve a phone call or letter telling seniors that they've won a sweepstakes or lottery but must pay legal fees, taxes or shipping costs before claiming the prize.

Con artists try to get the victim to buy into the scam by "getting the person tied up in anticipation of how they're going to spend their winnings," says Sally Hurme, a lawyer with AARP's division of consumer protection.

"They're very good with their snake-oil pitches," Hurme says, because they make the same call up to 10 hours a day.

Once they've convinced you of your winnings, the fraudsters often urge you to withdraw money for the purported legal fees or shipping costs immediately — before you can second-guess your decision.

That was the tactic used with Tolhurst, the retiree in Santa Monica. After she received a phone call in April telling her she'd won a $2 million prize in a People magazine sweepstakes, she cashed out $6,800 from her credit card.

She was told to put the money — all single dollar bills, which are harder to trace — inside a magazine. Within minutes, she says, a courier came and picked the package up. Tolhurst called People a few days later and learned that the publication had no such contest.

She couldn't get the credit card company to reverse the transaction because she had taken out a cash advance. So she's having to deal with the ugly consequences. Tolhurst is paying about $150 a month on the now $7,000 credit card debt, which is mushrooming at a 24.24% interest rate.

She has, though, learned a valuable lesson. "I get every day these mailings telling me I've won this or that, and I know they're not true," she says.

Seniors should be suspicious of anyone who tells them they need to make an investment decision on the spot, consumer advocates say.

Check the credentials of the salesperson — with the SEC, NASD and state securities regulators — before putting money into any investment. And don't think that just because you're fairly investment-savvy, you won't be victimized. A study by Wise Senior Services, funded by the NASD Investor Education Foundation, found that seniors who fall prey to fraud tend to be more financially literate than non-victims are.

Why? "Individuals like to think they're more knowledgeable than they are," says Grace Cheng Braun, CEO of Wise Senior Services in Santa Monica. "They know enough about investments that they think they can handle it."