CBS Local — Ransomware, the malware hackers use to lock victims’ computers and demand money to unlock them, has garnered more than $25 million in payments for those responsible for deploying viruses in just the last two years, The Verge reports.

A study on 34 separate cases of ransomware by researchers from Google, Chainalysis, UC San Diego, and the NYU Tandon School of Engineering were able to better map out the ransomware underworld.

Specifically, they discovered Locky, a strain of ransomware that has alone accrued more than $7 million in payments.

“Locky’s big advantage was the decoupling of the people who maintain the ransomware from the people who are infecting machines,” said Damon McCoy, a professor at NYU who worked on the study. “Locky just focused on building the malware and support infrastructure. Then they had other botnets spread and distribute the malware, which were much better at that end of the business.”

Ransomware is a scary byproduct for many and is becoming more and more frequent as the digital world continues to evolve.

Antivirus software is the main defense against ransomware. It blocks similar codes to known ransomware viruses but hackers have adapted by creating ransomware that will automatically change its code once detected.