What addresses to put on my NEW black list?

Trying to create a blacklist for my network.  Want to include
addresses for mainly streaming audio, and file shareing.  I have a
couple of network abusers who listen to internet radio that just don't
follow company policy which has banned it.  Yes I know I should try
and bust them but thats a pain in the butt and besides if I do that I
don't get the joy or experience of doing this.

First off I was going to deny the addresses of various "bad"
severs/web sites on the net at my firewall.  I was then going to
create a DNS entry that points all restriced IPs to a internal web
server that would host a page stating that the site is banned
(blackholing IPs).

As mentioned above the issue I have is finding the IP addresses to
ban.  Any help would be appreciated.

Thanks!

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