Bill Whitaker’s nightmare began on a Tuesday. His wife, Susan, didn’t learn about it until Friday.

Bill, 75 at the time, had received an email receipt for an upgrade to software he used to manage the books for his son’s company, but he knew he hadn’t bought the product. He called to get a refund and was told he needed to pay $500 upfront, install an application on his computer and turn over personal information, and then he would get it all back.

It was a scam.

By the time he told Susan three days later, some $28,000 had slipped from their accounts. The bank recovered $8,000 early the next week, but $20,000 was gone — critical life savings that Bill had been counting on to buy medications.

His son wouldn’t let him work for the company anymore. He began to ration his prescriptions, and he became afraid to read emails or answer the phone.

“He sort of stopped living,” Susan Whitaker told senators on Thursday. “He was so ashamed of what he had done that he just made himself not available to people.”

Older Americans are at the spear tip of what experts describe as a “tsunami of fraud,” most of it run by scammers operating abroad, often with the backing of organized crime syndicates and sometimes with the backing of adversarial nations.

Scams include bogus technological support, fake romances and AI-powered operations that clone the voice of a supposedly kidnapped child or grandchild, followed by a demand for money.

The Federal Trade Commission said consumers reported losing more than $10 billion to fraud in 2023. Actual losses are orders of magnitude higher because most victims don’t report it. One expert told Congress they hear about just one case out of every 20.

Because the fraudsters are usually overseas, little money is ever recaptured.

“When these criminals receive the money, it is gone. Almost impossible to get back,” said Sen. Mike Braun, Indiana Republican. “The only way is to prevent it once it starts to occur.”

Congress is conducting hearings on the issue this week in the House and Senate. Solutions have included better financial literacy, more warnings from banks and other financial institutions, and more regulations on industries, including banks and cryptocurrency.

Still, experts saw little hope of turning the tide in the near term.

Kathy Stokes, AARP’s director of fraud prevention programs, said scammers know what works because they “know how to exploit the human brain.”

People can quickly find themselves in unthinkable situations.

She recounted the story of a college professor snared by a pop-up message on her computer. Four and a half months later, when it was all done, she had needed to retire, emptied her accounts, and piled gold bars into a stranger’s van.

Scott Pirrello, head of elder abuse prosecutions at the San Diego district attorney’s office in California, told of a 94-year-old Air Force veteran who lost $143,000 in five separate cash pickups over two weeks.

Susan Whitaker said her late husband’s scammer had partial control of his computer while he tried to Venmo the initial $500 payment. When the money was about to be sent, she said, the scammer quickly added another zero to the total, making the payment $5,000. He then said he needed $5,000 upfront to get it all back, and it spiraled from there.

She was lucky to get back $8,000 of the losses because the money hadn’t all been withdrawn yet.

Mr. Pirrello said banks can usually do little because the customer walked in and withdrew the money. That makes it different from identity theft, which can be remedied.

In some scams, older Americans are purely pawns.

This year, a federal inspector general warned that fraudsters were calling and texting Medicare enrollees saying they qualified for a urinary catheter at “no cost” and just had to provide their information. The scammers would then use that information to begin billing Medicare for the devices, which, in many cases, weren’t even provided.

Nancy Gilmer Moore, who works for the Indiana Association of Area Agencies on Aging, told senators she was the target of that scam. Medicare paid the fraudsters $1,500 a month before she noticed it on her statement.

That nationwide scam is estimated to have netted nearly $3 billion for fraudsters.

Ms. Moore said scammers have moved on to a similar scheme involving billing for ostomy supplies.

Senators said the shame of being victimized is compounded for some who liquidate their investments and retirement accounts to give the money to scammers, only to find out they owe taxes on the income from the investments they cashed out.

“It’s revictimization, plain and simple,” Mr. Pirrello said. “They’ve had everything stolen from them, but the IRS sees that as income and taxes them on it.”