The recent discovery of Shellshock, the bash shell bug, has something in common with the discovery of Heartbleed earlier this year. Both vulnerabilities existed for many years before they were discovered – over two years for Heartbleed and over 22 years for Shellshock. Both affect a very large number of computer and communications systems. Both have induced a gut-wrenching panic.
There will always be two periods during which you are vulnerable to such exploits. The first is the period before the vulnerability is reported and may have been exploited by a few attackers. The second is the span of time between when the vulnerability is publicly reported and before you patch the affected systems. During this second period, every attacker imaginable will attempt to exploit the vulnerability. Predicting when new vulnerabilities will appear and what ways creative attackers will come up with to exploit them is generally a losing battle. That doesn’t mean there is nothing you can do to catch them.