Alternatively known as a spike guard or surge suppressor, a surge protector is a plug-in device designed to protect a computer from surges and spikes. The picture shows a Belkin power strip and surge protector, which can protect up to seven devices.
In 2009, Underwriters Laboratories published UL 1449, a standard which defines how surge protectors should be used safely. This standard allows no more than 500 maximum volts to pass through the line and is something to look for when purchasing a surge protector. Other things to consider is the surge protector response time, which should be less than one nanosecond and the Joule rating, which should be a rating of at least 200.
While it is important to protect your computer and computer peripherals, it is also important to protect your computer modem and network card. Surges not only have the capability of traveling over the power lines, they can come over any line that's coming from outside your home or business.