In July, a woman in Bakersfield, California was charged with elder abuse after her 73-year-old mother was found living in a decrepit one-bedroom apartment with no working plumbing and a rodent infestation. While the exploitation of senior citizens is rarely this egregious, it's surprisingly common. According to a 2013 study, elder abuse and neglect are estimated to affect between 700,000 and 1.2 million elderly people a year.

The annual cost runs in the tens of billions of dollars. And an important subset of that abuse is financial, targeting people's retirement security and life savings. Last year, Consumer Reports recapped a recent survey of 2,600 financial planners, and the findings were astonishing: "56 percent said they knew older clients who had been subject to unfair, deceptive, or abusive practices. Among reported cases, the average loss estimate was $140,500."

In June, the Senate appropriated $10 million for a new "elder justice initiative" to better prevent, investigate and prosecute abuse, including financial abuse. Better legal definition and stricter enforcement could help, but until that happens the best defense is to inform yourself and your loved ones of potential threats, and what to do about them. Here are some of the most common sources of financial vulnerability that senior citizens face.

--Over the phone, by mail and email

Older people are often targets of "phishing" or "social engineering" scams. They may be contacted by someone posing as their bank asking them to confirm account information, or someone saying they have won a lottery or sweepstakes and need to provide personal information to claim a prize, or soliciting for a fake charity, or to settle a debt or a hospital bill. Or the scam may be a sob story from someone asking for help, or even from someone in an online chat room posing as a romantic interest.

The rule to prevent these approaches is simple. Never give out any personal information, including your name, address, Social Security number and account numbers, to anyone who calls you or emails you. If you go to your bank website, type in the address yourself. If someone calls or emails claiming to be from your own bank, hang up, look up the real number, and call them back. If you have a family member who may be vulnerable to this kind of scam, ask for them to agree to tell you before giving out their information to anyone. Sign up for the AARP's "Fraud Watch Network" to get regular email alerts about the latest scam.

--Bad advisers

After scams, the next level of financial exploitation comes from deceptive marketing of bad financial products. In the survey mentioned above, 73 percent of financial planners knew of older investors who had been invited to so-called "free meal" seminars, designed to market products such as annuities, reverse mortgages, life insurance and mutual funds. These are often overpriced, loaded with hidden fees, or make false promises about being "low-risk" or "no-risk."

As a rule of thumb, if someone is giving you the hard sell about any financial product, they probably stand to make money. Truly low-cost investments such as index funds don't have armies of salespeople. Your bank, credit union, seniors' organization, community group or church may be a good source of referrals to a fee-based certified financial planner or adviser. The federal Consumer Finance Protection Bureau has resources dedicated to helping older Americans make financial decisions. (Visit http://www.consumerfinance.gov/older-americans.)

--Family abuse

The most heartbreaking form of exploitation happens between seniors and family members or friends. According to a 2011 analysis of reported cases, about 34 percent of the perpetrators of elder financial abuse were known to their victims, a number that went up around the holidays.

Older people who are living alone, socially isolated, and/or depressed are more likely to be victims of abuse. If a friend or relative is pressuring you for money, seek support elsewhere. If you have an elderly relative, watch out for signs like a sudden decline in your family member's standard of living or someone else getting access to their bank statements.

(Anya Kamenetz' latest book is "DIY U: Edupunks, Edupreneurs, and the Coming Transformation of Higher Education." She welcomes your questions at diyubook@gmail.com)