Summary

Because new DoS attacks surface periodically (one every few months), your best defense is to keep current on advisories and patches.

However, some words of warning: Such attacks come in waves and often mutate. teardrop.c is a good example. Initially, teardrop.c's release caused widespread havoc and sent system administrators diving for patches or fixes. Many system administrators assumed that once such patches were in place, all was well. All was not well. Shortly thereafter, teardrop.c mutations began appearing.