Who's the first Hacker anonymous?
It is not possible to identify the first Hacker Anonymous because:
a) the postings are "anonymous"
b) the Anonymous Hacker attacks were the result of an evolved, cooperative (but anonymous) environment with (possibly) no single individual responsible for the first attack.
The Anon sub-culture developed around a manga-anime imageboard, 4chan, created by Christopher Poole in 2003 which allowed anonymous posts and sharing.
To the best of my knowledge, Christopher has not been identified as an Anon. 4chan is still (again, to the best of my knowledge) still primarily a manga-anime website.