If you think about catching a cold, you know you feel miserable, but you don't have a clue how you got it. You can catch a cold from standing close to someone who's sick or turning a doorknob that they touched.

That's similar to how airborne viruses infect computer systems with malware. These viruses spread over Wi-Fi connections, from one computer to another.

That's what's happening with a virus that can be transmitted through billions of wireless keyboards and computer mice. That's according to cybersecurity firm Bastille, which reports that wireless devices that do not use a Bluetooth connection are at risk of spreading the MouseJack virus.

All a hacker needs to get into your computer is a $15 dongle and few lines of computer code. The hacker intercepts your computer dongle's radio frequency.

Here's how it works. When you're using a wireless keyboard or mouse, you have a dongle that listens for its radio frequency. When you type in something or move your mouse, the dongle picks up that message and makes the appropriate action.

Hackers are intercepting radio frequencies using the 2.4GHz ISM band. Unlike Bluetooth, there isn't an industry standard to protect your devices. So, manufacturers create their own security system, if they have one.

This vulnerability affects Windows PCs, Macs and Linux computers. It also affects several types of wireless keyboards and computer mice, including Dell, Lenovo and Logitech. (See link to complete list below.)

Once the hacker is in, they gain full access to your computer, although they need to be within about 100 meters of you. They can take over your computer and infect it with malware.

To protect your devices: To find out if your device is at risk, click here for Bastille's list of affected devices. If your wireless device is at risk, contact the manufacturer, and ask if a firmware patch has been issued, or if one is planned. If not, switch to a Bluetooth-connected wireless keyboard or mouse. And always make sure you're using a strong Internet security system.