With the invention of bitcoin, Ransomware was made possible. Prior to bitcoin it was difficult for the bad guys to get paid as it was easy to follow the money back to them. With bitcoin it is very difficult to impossible to follow the money back. Ransomware is a form of virus or malware that infects a computer and encrypts all of your documents, pictures and even music and videos on your computer and generally will then go out over the network and encrypt any other resources that it can find. They then ask for money to give you the keys to unencrypt your information. This has been the single biggest problem for a number of years and there are many of knock-off versions of the original which were not as well written as the first and have caused even more problems in that, even after paying the ransom, people have not got their data back due to several errors in the process.