MOORE, Oklahoma - Lesson plans and other important documents are being held hostage by hackers. A malware virus invaded Moore school district's public drive Wednesday.

The district's IT specialist continues to work on restoring the infected drive. But how it became infected is still unclear.

Moore Public Schools is the latest victim to cyber extortionists. The district discovered the virus around 8 a.m. Wednesday.

“Once the virus was located the director of technology shut down every server," said Dustin Horstkoetter, Moore Public Schools.

But, files are now held hostage by cryptolocker, a type of randsomware that holds files captive unless you pay for the key to unlock them. Many teachers are now forced to redo weeks of lesson plans.

Experts say unfortunately ransomware is becoming more prominent and profitable.

"They are not really after to steal your data. They are there to make revenue," said Mark Gower, Oklahoma's chief information security officer.

Emails are the most common our computers are infected with randsomware. Hackers pose as someone you know, like a family member, a friend, or even a coworker. When you go to click on the email and any attachments inside, that's when they infect your files.

To protect your computer and files, Gower says never click on the link from an email rather go to the site yourself. Never download an executable files. Change your passwords regularly and back up important files regularly.

“If you do get hit don't pay the extortion. Because you are just funding further cybercrime,” said Gower.

If your computer does become infected, always report it to police and the FBI internet complaint center.