very heavy load avarage

[Riccardo Giuntoli]

Hi folks,
i've got a server with FreeBSD 5.4-STABLE and pf with a gigabit
ethernet interface directly on internet. Two C class are routed over
it, and i sell shell account for irc processes. As you know on irc
many times the server is under DDOS attack many time up to 100 mb/s.
But with one gigabit connection the problem isn't the band of the
attack, my server's cpu load avarage goes extremly high, you can
verify here:

http://www.6shells.net/graphs/graph_14.html

What can i do for decrease it?
Please help,
Regards

Name: Riccardo Giuntoli
Email: taglio at gmail.com
Homepage: http://www.luxoro.org/
Location: Genova, Italy
6BONE Handle: RG581-6BONE
PGP Key: 0x67123739
PGP Fingerprint: CE75 16B5 D855 842F AB54 
                          FB5C DDC6 4640 6712 3739
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