Regexp for blocking dynamic hosts?

[Patrick Lists]

Hi,

I got a lot of spam lately from dynamic hosts so gradually I have been 
adding rules to block them with the help of the rules from
http://gabacho.reto.jp/en/anti-spam/anti-spam-system.html
Unfortunately this type keeps slipping through:
Received: from 200-161-108-143.dsl.telesp.net.br

My regex foo is pretty non-existant. Does anyone know what regexp line 
would block such a hostname?

Thanks for any pointers.

Regards,
Patrick