list of zombie masters to block
these are the addresses of spamzombie masters, they make sure that their zombies (your pc) receives the spam to send to others (spambot).
The internet storm center published the list because the number of viruses with spambot strategies is increasing (as some spammers get caught and punished).
Another tip is to stop all dns traffic to other servers than those that you know very well (yours or those of your ISP). Those spambots install sometimes also a dns server on a zombie. The reason is that relaying hundreds of those spambots the investigators get nowhere near the real master of the zombie network.
This is the list. You can start by blocking it in your firewall or proxy. It is quite long (and that shows the extent of the problem). >http://isc.sans.org/diary.php?date=2005-04-11
my personal opinion is that it is up to the ISP's to block or present a preventive warning or confirmation page for this kind of addresses about which there is no doubt whatsoever that they used for criminal purposes (as spamming is an offense now in most of the countries) without the knowledge of the personal user or network administrator