It is nicknamed “creepware,” and more than half a million people around the world have been prey to its silent computer snooping.

An international crackdown by the FBI and police in 19 countries has brought more than 90 arrests in what authorities say is a serious strike against a widespread and growing problem.

U.S. Attorney Preet Bharara in New York told reporters the global investigation “exposed and crippled a frightening form of cybercrime that has affected hundreds of thousands of users around the world.”

The sweep, capping a two-year operation, was coordinated so suspects didn’t have time to destroy evidence. It included the arrest of a Swedish hacker who was a co-creator of Blackshades, Alex Yucel, who was apprehended in Moldova.

In total, one of the largest global cybercrime crackdowns has yielded the arrests of more than 90 people linked to the Blackshades malware, with more than 300 searches conducted, Bharara said.

The malware, which sells for as little as $40, can be used to hijack computers remotely and turn on computer webcams, access hard drives and capture keystrokes to steal passwords — without the victim ever knowing it.

According to Bharara and the FBI, criminals have used Blackshades for everything from extortion to bank fraud, and it has become one of the world’s most popular remote administration tools, or RATs, used for cybercrime in just a few years.

“The RAT is inexpensive and simple to use, but its capabilities are sophisticated and its invasiveness breathtaking,” Bharara said. “For just $40, the BlackShades RAT enabled anyone anywhere in the world to instantly become a dangerous cybercriminal, able to steal your property and invade your privacy.”

To prove his point, the FBI released screen grabs showing how the malware works, including an ungrammatical message that would pop up on the computer screens of victims that said: “Your computer has basically been hijacked, and your private files stored on your computer has now been encrypted, which means they are impossible to access, and can only be decryped/restored by us.”

CNN