Brace for plenty more scams—many of them far more sophisticated. The pandemic has been great for Amazon, Netflix, Peloton, and Zoom and also for a group of entrepreneurs seeking far less attention: corporate fraudsters. We may not know their names yet—except for a few—but we can be certain they’re hard at work, because the pandemic may be the greatest environment for business fraud in decades.

We’re not talking about defrauding individuals, though that business is booming also as bad guys prey upon fearful consumers with scams involving bogus COVID-19 treatments, worthless PPE, and nonexistent charities. Rather, we’re talking about defrauding businesses, investors, and governments. For that line of work, the pandemic is uniquely wonderful, creating a rare conjunction of factors that produce an especially fraud-friendly climate.

Tough times. Fraud experts say every corporate fraud grows from a combination of three elements: pressure, opportunity, and rationalization. A bad economy creates pressure. Companies may run short of cash or may be unable to meet Wall Street’s expectations, so they resort to trickery. For example, when WorldCom was desperate to hide its faltering performance in the dotcom bust, CEO Bernie Ebbers capitalized expenses, intending to spread them over years of financial statements rather than report them properly in the quarter when they were incurred. Convicted of fraud, he had served 13 years of a 25-year sentence when he was released from prison last December, shortly before he died.

Where is the financial pressure heaviest in the pandemic? The worst-performing sectors of the S&P 500 have been energy, financial, and industrial, but glamorous companies can also be strong candidates for fraud if managers fear next quarter’s financial results won’t support the high-flying stock.

Less oversight. The second element of fraud—opportunity—widens when people know they’re not being watched. Dorris’s organization, the ACFE, reports that some financially stressed companies have cut anti-fraud staff and budgets. More broadly, with millions of employees working from home, especially if they work entirely with numbers, oversight and security may not be what they are in an office building. Large majorities of the ACFE’s members say reporting, detecting, and investigating fraud have become more challenging in the pandemic.

One reason committing fraud is easier in the pandemic—in fact the main reason cited by ACFE members—has nothing to do with technology. The problem is that it’s now harder for examiners to travel and interview people in person. “Our fraud examiners want to see whether [interviewees] are closing their arms, for instance. Are their legs doing something? What about micro-expressions in the face and how muscles in the face contort?” says Dorris. “Zoom is good, but it’s not the best.”

This is part of what makes the pandemic environment so unusual. Oversight usually intensifies in tough times, as managers scrutinize every deal and every dime. But this time, opportunity to misbehave has expanded along with pressure to do so.

Fast, free money. The Paycheck Protection Program—necessary and effective though it was—transformed 2020 from a merely rich environment for scamming into a true festival of fraud. Over a half-trillion dollars was loaned to small businesses last spring and summer with little or no verification of applicant information. Vetting wasn’t possible; on May 3, the Small Business Administration’s busiest day, it approved 514,000 loans. Massive fraud was inevitable—the Justice Department set up a PPP team the day the program was established—and is increasingly coming to light.

We may never know how much money was given to fraudsters, but the early cases are suggestive. For example, a Miami man has been charged with borrowing $3.9 million in PPP funds by filing a fraudulent application, then buying himself a Lamborghini Huracán Evo for $318,497; the feds took the man and the car into custody. The FBI has opened hundreds of PPP fraud investigations, likely a small fraction of the frauds included in the SBA’s 5.2 million PPP loans.

The year 2020 will be remembered for many things, mostly awful. Fraudsters are among the few who will look back wistfully, thinking: “Those were the days.”

More health care and Big Pharma coverage from Fortune:

• Creating a COVID vaccine is only half the battle
• Biden’s COVID-19 task force is 38% female and 69% underrepresented minority
• Infectious disease experts are very excited about the Pfizer and BioNTech vaccine
• We don’t know enough about COVID antibodies to count on them
• U.K. to use A.I. to spot dangerous side effects in the millions of COVID-19 vaccinations it will deliver