A new report from Check Point Research says there has been a surge in fake vaccination certificates online, via the darknet. Users send their details and $200 to hackers and, in return, receive an official-looking vaccination card.

There’s also a strong market for negative COVID-19 tests among travelers, including a “buy two, get the third for free” deal. Those falsified results can be purchased for $25 in less than 30 minutes.

Check Point says advertisements for fake vaccination documentation are up 300% since January. More worrisome, there’s also a growing market for counterfeit coronavirus vaccines.

The darknet isn’t visible to search engines, but hackers and other online ne’er-do-wells gather there to do everything from exchange stolen credit card numbers, sell drugs, and shop new malware.

Researchers say they saw over 1,200 advertisements for vaccines on the darknet, with counterfeit versions of the Oxford-AstraZeneca and Chinese Sinopharm shots selling for $500 and counterfeit Johnson & Johnson selling for $600. The Russian Sputnik vaccine is also advertised for $600. Some hackers were charging as much as $1,000 per dose.

“The darknet is booming with activity related to the vaccines,” said Oded Vanunu, Check Point’s head of products vulnerability research, in a statement. “This wasn’t the case when we first started to study the darknet around this topic three months ago…Cybercriminals are looking to capitalize on the public’s interest to both get the vaccine or avoid the vaccine. It’s imperative for people to understand that attempting to obtain a vaccine, a vaccination card, or negative COVID-19 by unofficial means is extremely risky, as hackers are more interested in your information and identity for exploitation.”

Researchers say they expect activity surrounding forged documents and counterfeit vaccines to increase in the coming months—and warn people not to post their vaccine cards or negative COVID-19 test results online, as those are making their way onto the darknet.