300MB and memory bursts

Hi,

I am running the latest WP on a dreamhost VPS with the minimum 300MB of memory. It is a small site with less than 100 “real” visits per days (maybe even less than 50). But the thing is that some bots are visiting the site more that 300 times within minutes. And that makes the server’s memory bust.

So I read the log files and query entries to find the guilty IP host to block it but either sometimes the host is : 26.236.236.104.in-addr.arpa. not found: 3(NXDOMAIN), either there is always a new IP that comes up and busts the memory allocation.

300MB is supposed to be plenty.

Why does the memory busts like that every week and what should i do to avoid it?

thanks