On Sun, 23 Sep 2007, Chad Perrin wrote:
In the case of that "private zero day exploit", then, nobody will ever know about it except the person that has it waiting in reserve -- and if someone else discovers and patches the vulnerability before the exploit is ever used, it never becomes a "public" zero day exploit. In other words, you can always posit that there's sort of a Heisenbergian state of potential private zero day exploitedness, but in real, practical terms there's no zero day anything unless it's public. The moment you have an opportunity to measure it, the waveforms collapse.
The exploit is not made public by its use. The exploit is not even made public by (back-channel) sharing amongst the hacker/cracker community. The exploit is only made public if detected or the vulnerability is disclosed. Until detected/disclosed the hacker/cracker can use their 31337 0day spl01tz to break into whichever vulnerable machines they like. 0day exploits are valuable because the opposition is ignorant of them.
Posting exploits to BUGTRAQ, however, inherently makes them not 0day...
