Many people’s personal information is readily accessible to hackers, amassed from dozens of data breaches over the past few years. Last month, Experian, the credit reporting agency, found a fresh batch of stolen data for three million people, containing all the pieces of personal information that a scammer would need to file for their stimulus checks.

The coronavirus has made it even easier for fraudsters to get more information. Many are bombarding Americans with emails and phone calls that use the uncertainty around the virus to distribute malware and get people to divulge their bank information and other data, which can then be used to defraud the same people. Google said it intercepted 18 million such emails last week.

Now criminals are deploying those troves of information to get their hands on the checks that the federal government is sending to needy Americans. Over the last month, more than 22 million people have filed for unemployment benefits.

Stimulus funds are separately expected to go out to around 150 million people. While the Treasury Department electronically deposited the money for around 80 million people who have bank accounts on file with the government, the I.R.S. created an online portal for the 70 million or so other recipients who did not have that information on file.

The portal allows people to enter a new bank account address for the government to send them their money. But it requires only a few pieces of data for verification: a Social Security number, an address, a phone number and a date of birth.

Security experts said that the I.R.S. had opened up the door to fraud by requiring so little data to claim the money. “The stimulus site is a little bit like ringing the dinner bell for hackers,” said Brian Stack, the vice president for dark web intelligence at Experian.

The I.R.S. did not respond to request for comment.

On forums on the darknet, where criminals gather to buy and sell identity information and discuss tactics, fraudsters have openly discussed the opportunities presented by the stimulus funds and unemployment benefits.