Part of this drive results in an ultim ately beneficial co-evolution of security through com petition between attacking hackers and defending hackers. Just as the speedy gazelle adapted from being chased by the cheetah, and the cheetah becam e even faster from chasing the gazelle, the com petition between hackers provides com puter users with better and stronger security, as well as m ore com plex and sophisticated attack techniques. The introduction and progression of intrusion detection system s (I DSs) is a prim e exam ple of this coevolutionary process. The defending hackers create I DSs to add to their arsenal, while the attacking hackers develop I DS-evasion techniques, which are eventually com pensated for in bigger and better I DS products.