Look for a UL listing of 1449. Clamping voltage should be no higher than 330 volts. It may be hard to find out, but try to determine if the surge protector you are buying uses thermally-fused MOVs. Make sure that any device you buy has an indicator light or an audible alarm that lets you know if the suppressor is not functioning correctly or is improperly grounded. Surge protectors with alarms are especially useful if the device is hidden behind furniture or equipment.
Computer networks have special surge protection needs.
Contact a computer network specialist for advice concerning surge protection for networks.