An 86-year-old Oakland woman doesn't mince words when it comes to con artists.

"I think they're scum," she said, "but they're very clever. They tell a convincing story."

The woman received a call in July from a man purporting to be her grandson, who lives in another state. He said he had been arrested in Canada for fishing without a license and needed $2,800 for bail. He begged her not to tell anyone.

The caller then handed the phone to a second con artist who pretended to be a Royal Canadian Mounted Police officer. The "Mountie" said the money must be sent via MoneyGram from a Wal-Mart. The woman did so.

Later that day, the "Mountie" and an "attorney" called back to say an additional $2,500 for a fine had to be wired. Again, she did so.

A few weeks later, she spoke with her grandson and learned she had been duped.

"I was stupid enough to fall for it," she said. "I should have known better. I would do anything for my grandson, so I was easy prey. But it won't happen again.

"I'm just glad it wasn't any more. I just want to forget that it ever happened."

A Crafton octogenarian likewise wants to forget about her experience this month when a "police officer" in Toronto called to say her grandson, who was being held incommunicado, had been speeding and drinking when he was involved in a vehicular accident.

She immediately wired $3,900 for "bail," and an additional $3,700 the next day to pay for damage to the other car in the "accident."

The woman, who took out a $4,000 bank loan to make the payments, called her grandson's cell phone. He answered at his job. She was happy he was safe and not in trouble, but was crestfallen at becoming a victim.

"It makes me sick. I have trouble sleeping," she said. "I panicked. I had to get the money. I think any grandmother would do that."

After she realized what had occurred, the con artists called again, saying her grandson couldn't leave the country without paying a $2,500 fine. She told them police were on the line, even though they weren't. The scammers hung up.

Joseph Vogel, of Carrick, was surprised when Moore Hingis from England responded to his ad offering piano lessons on Craigslist, the online classifieds site. Mr. Hingis said he wanted to send his son, Murphy, 14, to Pennsylvania with a nanny to study with Mr. Vogel, 40, who also is a caseworker for the elderly.

"It sounded too good to be true," Mr. Vogel said. But he corresponded by e-mail with Mr. Hingis, who wanted an estimate for five months of lessons. Mr. Vogel, who set his price at $220, was shocked when he received via Federal Express a Bank of America check for $2,300.

In an e-mail, Mr. Hingis explained the extra money was for the nanny and asked Mr. Vogel to transfer the difference to her by wire.

What had seemed a little fishy to Mr. Vogel now really smelled, and he went to the police. The check was counterfeit, but as often happens in these types of cases, looked authentic because of advances in home printers.

Such a scam is gaining in popularity, authorities said, as con artists troll classified ads looking for people offering goods or services. They send counterfeit checks for sums that are thousands of dollars more than what is being asked, then ask would-be victims to wire back the difference.

A variation: a check-cashing scheme in which someone looking for work is contacted by a "foreign business" that needs someone to cash American checks. The victim is sent authentic-looking checks for thousands of dollars, then is told to deposit them in an account, keep up to 20 percent and wire transfer the remainder back to the company. The checks are counterfeit or stolen.

Happy not to be among those victims, Mr. Vogel thought he'd have the last laugh.

"I forgot to tell you that I really don't teach piano," he wrote the con artist. "It's tuba lessons."

No word if Murphy has any interest in the tuba.

On Web sites and in e-mails, consumers are told they can qualify for a payment from President Barack Obama's economic stimulus package by providing a little information. But the promise of stimulus money in return for a fee or financial information is always a scam, the Federal Trade Commission warned earlier this month.

The Internet-based scam is designed to look as if it is from the Internal Revenue Service or a rebate company. Some use photos of Mr. Obama and Vice President Joseph Biden to increase the look of legitimacy.

E-mail messages may ask for bank account information, purportedly so the operators can deposit consumers' share of the stimulus directly into their bank account. Instead, using that information, they drain victims' accounts.

Some e-mail scams don't ask for information, but provide links to sites that supposedly offer information on how to qualify for funds. But by clicking on the links, consumers download malicious software or spyware that can be used to garner information used for identity theft.

Accountants aren't the only busy ones during tax season. Con artists seize upon desires of taxpayers to receive refunds quickly.

The IRS has identified 1,500 schemes in which con artists use the mail, the telephone, fax, e-mail and the Web while purporting to be IRS agents.

Generally, they seek a taxpayer's personal and financial information, claiming it is needed to provide tax refunds or offering other fraudulent reasons. The information is then used for identity theft and to access financial accounts.