ransomware

Ransomware is a subset of malware in which the data on a victim's computer is locked, typically by encryption, and payment is demanded before the ransomed data is decrypted and access is returned to the victim. The motive for ransomware attacks is nearly always monetary, and unlike other types of attacks, the victim is usually notified that an exploit has occurred and is given instructions for how to recover from the attack. Payment is often demanded in a virtual currency, such as Bitcoin, so that the cybercriminal's identity is not known.

Read on:

https://searchsecurity.techtarget.com/definition/ransomware