Sorry to upset you guys after you have convinced acf to resolve the post but surge protectors will not protect against a lightning strike in the vicinity. A strike, say on an electricity transformer directly supplying your home would blow the surge limiters in your protection device. Your modem would be the least of your worries; your computer would be high on the priority list.
They are really only for mains spikes which admittedly are the predominant cause of electronic failure.
However it is the best you can do for under £20. You should also have your equipment earthed separately via an earthling rod and not rely on the mains earth.
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