What began last year as a few bad apples falsifying COVID-19 tests to allow them to travel has turned into a full-blown thriving market.

The black market, that is.

The inception of travel restrictions in the wake of the coronavirus pandemic has led to a culture of cheating for many who want to fly, but can’t if they test positive for the virus, according to the news outlet Vice .

In short, if you’ve got the cash there are plenty of nefarious characters using Photoshop and Microsoft Paint to forge the documents.

Vice asked two such forgers how it worked and both – who asked to remain anonymous – were more than happy to give details.

“I just fired up Photoshop and changed the date,” wrote one man who had doctored results for an entire group of friends. “Fun fact, the document [test result] was in French whereas they were in Sweden the day it was supposedly made, but they didn’t see a problem in that.”

The other person took a slightly less sophisticated route and changed the date of an old test with Microsoft Paint for his vacation to Southern Europe.

The two aren’t alone. This week 40 travelers tried to present fake test results to get into Croatia, and earlier this year a Dutch teenager who had tested positive for the virus went a step further and falsified her result to escape quarantine in Switzerland. She was arrested just before boarding the plane.

The Vice report includes confirmation from a spokesperson with the aviation industry group Airlines for America that staff members "tasked with verifying that a passenger has a legitimate test result do not receive any specialized training."

The respected travel guide Frommer’s said part of the problem is that COVID-19 tests are not universal and come in different languages. Frommer’s said the need to standardize test results grows more urgent on January 26, when the United States begins requiring negative COVID-19 tests of all who enter from abroad, including U.S. citizens returning from vacation.