First of all, you need a reliable anti-spyware program, which is kept up-to-date. Secondly, make sure you stay away from illegal websites, fake updates and spam. At the moment of writing, spam acts as the main source of ransomware. Finally, back up your valuable data (business documents, photos, music files, art, etc.) to prevent its loss. If infected, you should disconnect your PC from the Internet to stop the encryption process. Then, remove infected files and restore your files from backup.