These are the five worst we've seen so far in 2015.

These are the five worst we've seen so far in 2015.

Rombertik's Endless Loop

One of the greatest hooks of "Mission Impossible" is its memorable reminder: "this message will self destruct." The Rombertik virus took this to heart, being coded to sabotage a computer and render it unusable if it is discovered. Unlike the notes in the Tom Cruise movie franchise, however, it doesn't actually explode. But if it is found, it deletes key boot files in Windows so that the computer then starts and re-starts on an endless loop. The machine is rendered useless and the virus lives on. Charles Darwin would even be impressed at this artificial intelligence's determination to survive at any cost.

Lenovo Sells Computers that are Already Infected

Earlier this year, Lenovo sold its customers computers that were already inflicted by "Superfish" adware that disables a web surfer's ability to use secure connections. It automatically breaks all attempts at safe browsing (through HTTPS) and thereby leaves people badly exposed to all sorts of evildoers. One cyber security expert wrote that Lenovo's negligence or stupidity or maliciousness -- nobody was exactly sure which — was "quite possibly the single worst thing I have seen a manufacturer do to its customer base."

Android Gets "Stagefright"

While viruses and bugs have traditionally attacked computers, mobile phones are increasingly being targeted as consumers continue to ditch larger devices devices. Joshua Drake of the firm Zimperium uncovered one enormous vulnerability in the Android operating system that he says left some 95 percent of phones on this platform vulnerable to a hacker remotely accessing the device's microphone, camera, and external storage. Fortunately, he informed Google about the hole this spring — well before making the information public — so the company has circled the wagons and fixed the issue for some devices. But the exploit remains for many who use Android, and many are likely being attacked right now without even knowing it.

Cryptolocker Forces Australians to Pay

Hackers stuck the shores of Australia with a lethal virus known as Cryptolocker. This ransomware is considered to be unbreakable and forces users to either pay up or forever lose access to irreplaceable files. According to the Australian Competition and Consumer Commission, more than 2,500 Aussies have fallen victim and coughed up almost $400,000 combined to the enterprising hackers.

Thunderstrike 2

The biggest news in malware this year may not come from actual malware. A team of "white hat" hackers have found a way to exploit the Apple operating system, which was once considered virtually invulnerable to attacks. They first found a way into the infrastructure in 2014, but it wasn't until recently, with Thunderstrike 2, that they found a way to make this "firmworm" jump from computer to computer. (The previous incarnation required physical access to a single machine.) So far, this type of attack is still in the hands of the good guys, but it is a wake-up call for a company that has made a reputation out of being infinitely more secure than its PC rivals.