NEW YORK - When a New York City jury recently convicted Anthony Marshall, 85, the only child of millionaire-socialite-philanthropist Brooke Astor, of 14 counts of fraudulently squeezing huge sums out of his late mother's $180 million estate, many observers thought it was simply an isolated case of financial patricide among the super rich.

No way!

Abuse of wealthy elderly parents by their greedy adult children and other relatives is as common as sin - so common that legal eagles have coined a name for it: elder abuse. More than 500,000 reports of such abuse against elderly Americans are sent to legal authorities every year, and millions more cases are thought to go unreported. Indeed, U.S. Senate sources estimate that only 16 percent of all elder abuse cases are reported.

A comprehensive survey by the MetLife Mature Market Institute concludes that financial loss by victims of elder abuse is at least $2.6 billion a year. Figuring that there are still plenty more cases to be found, district attorneys have set up their own elder abuse offices in New York, Los Angeles, San Diego, Brooklyn, Seattle and many other places.

While elder abuse commonly involves a relative of the victim, there are plenty of other hucksters after older folks' dough. There is an endless variety of telemarketing fraud alone; offenders simply make cold calls to solicit money for all manner of fraudulent investments, insurance policies, travel packages, mortgage fraud and predatory lending.

As for the victims, older people control the largest single share of the nation's personal wealth, so they are obvious targets for predators.

Legal authorities say that the fraudsters themselves tend to betray certain characteristics. For example, they show an excessive interest in the targeted older person's assets, demonstrate excessive control of an older person, act hostile during appointments or on the phone and try to control telephone use.

To prevent becoming victimized yourself by elder abuse, you simply must practice basic caution. For example, do not leave items of value out in the open. Beware of advisers who try to control you during interviews. Beware also of advisers who attempt to overcharge you, or use "out of sync" bank checks.

Here are some thoughtful recommendations from California Advocates for Nursing Home Reform:

- Document financial arrangements. Put all financial instructions in writing. Keep updated records of all financial transactions in a safe place.

- Practice preventive banking. Use direct deposit. Keep checks in a safe place and don't sign a blank check allowing someone else to fill in the amount. Never give someone your ATM, credit card or PIN or Social Security number. Check your bank statements carefully for unauthorized withdrawals. Be careful of joint accounts as both parties have equal access to the money. When in doubt, contact the bank to stop payments or checks, to flag or put a hold on the account or to close an account.

- Be cautious of signing powers of attorney. Before signing a power of attorney for a bank account, general purposes or for financial management, know and trust the person that you are naming as the agent.

- Be aware that a power of attorney is a powerful legal document. It sometimes can be used by unscrupulous persons to "legally steal" someone's money and assets. Consult an attorney or make an appointment with legal services before executing power of attorney.

- Establish relationships with financial professionals. Get to know your bank, attorney and financial officers. They can help detect changes or unusual activity that might signal extravagant promises.

- Be aware of scams. Just say no to bogus prize offers, travel packages, get-rich-quick schemes, and even ideas plucked from unknown charitable or religious organizations in telephone solicitations. Never give your credit card or Social Security number over the phone.

- Check your health-care bills, question bills or notices for services that you do not understand and report providers that have suspicious billing practices. Also, never give your Medicare number to unauthorized providers for "free" health care services.

Most of the above may seem familiar, but as many a victim of elder fraud can tell you, it's better to be safe than sorry.

(MarketWatch reporter Bao Ong in New York contributed to this article)

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