Ransomware is a category of malicious software that is becoming increasingly widespread. It differs from other kinds of malicious software in that its primary purpose is to render the victim's data files unusable (typically by encrypting them) until a "ransom" in difficult-to-trace virtual currency such as Bitcoin is paid. Organizations all over the world, including hospitals, police departments, and universities, have fallen victim to ransomware attacks. Affected systems to date have included Windows workstations and servers, Macs, linux workstations and servers, unpatched wiki or blog software, Android phones, and any data volumes these devices are able to access (e.g., external hard drives, network drives or file servers).
For advice on how to protect yourself from ransomware, please visit http://imss.caltech.edu.