"Ransomware is a type of malicious software that blocks access to the victim's data and threatens to publish or delete it until a ransom is paid", according to Wikipedia. Here is the full article.
A recent www.SmartMeetings.com article offers great tips for Meeting and Event professionals to guard against such attacks. Read the full article here. We also highly recommend this Event Manager Blog article on event digital security. Another library of ransomware stats is available from Comparitech.