Security experts have long touted a layered approach to cyber security as the most effective way to thwart network intruders. But a new study shows that layered security can be less effective than expected. Only three percent of products from 24 vendors were able to detect the 1,711 known exploits used in the test. One pitfall to avoid with layered security is using products from the same vendor, NSS Labs research director Stefan Frei said. “You have to be very careful to choose vendors that put the best intelligence into their products,” he said.”]