NGiNX to prevent DDoS

[Juergen Gotteswinter]

Hello Folks

i got setup where nginx acts as reverse proxy for 3 apache backends. 
yesterday we had the case that some kind of bot or spider started 
attacking one domain which gets through nginx.

is there any possibility to configure nginx for something like "rate 
limiting" or should i better go with iptables? the hardware is strong 
enaugh to take this (quadcore xeons).

Greetings

Juergen