Before the development of the modern, long-range defensive weapons, one common military tactic -- dating back to the days of ancient Greece -- was to launch "human-wave" attacks. Basically, just sending in huge numbers of footmen, without any fancy weapons or organized strategy. Although casualties among wave attackers were high, they often found weak spots and managed to penetrate defenses.

Since 2001, when the first worms began to assault networks worldwide, modern attackers of network security have been using a version of this ancient military tactic. To date, they have unleashed three successive waves of attacks, each managing to penetrate vulnerable parts of the network. However, one key difference between these attacks and ancient ones is that network hackers have become increasingly sophisticated and have continually adapted their methods as defenses have tightened.

For organizations trying to shore up network defenses, it's important to understand how the security threat landscape has evolved. Only then is it possible to determine the best use of network-security solutions -- particularly Intrusion Prevention Systems (IPS) -- to block ongoing and future waves of attacks.