One of the resurgent threats on the web is ransomware. These programs will encrypt files on your hard drive and demand a ransom to send you a key to decrypt them. You either send bit coins or money to an address usually in Russia or Eastern Europe. If you pay the ransom you may receive a key to unlock your files. It is typical for many of these programs double the ransom if you wait a few days.
One of the first reported ransomware programs was the “AIDS” trojan in 1989. Since then they have become significantly more sophisticated. They now will search for any online back ups and encrypt those too. If you are using Time Machine, Carbonite, Windows Backup and any other online backup, it will encrypt them. Leaving you the choice of either losing your files or paying the ransom and possibly salvaging them.
You used to be able to avoid ransomware by not installing unknown software and avoiding questionable sites. Recently ransomware was reported to install via an exploit found in the flash player from well known sites including yahoo, match.com, AOL, and the Atlantic. It was additionally reported that yahoo ads, which is used by many well known sites, was tricked into serving some ransomware.
The best way to protect yourself from ransomware is to keep your browser, virus scanner, and operating system up to date. You also need to keep an offline backup of your important files. This could be as simple as a couple of usb keys you keep in a drawer.