limit_req per subnet?

[Grant]

>> I rate limit them using the user-agent
>
>
> Maybe this is the best solution, although of course it doesn't rate
> limit real attackers.  Is there a good method for monitoring which UAs
> request pages above a certain rate so I can write a limit for them?


Actually, is there a way to limit rate by UA on the fly?  If so, can I
do that and somehow avoid limiting multiple legitimate browsers with
the same UA?

- Grant