Invisible <voi### [at] devnull> wrote:
> If it blacklists the server IP addresses, all you need to do is copy the 
> ads to another server and the blacklist is defeated. As a bonus, if you 
> put the ads on the same server as the genuine content, then you *can't* 
> blacklist the server or you'll be blocking genuine content.

  The vast majority of ads come from external URLs. Only an extremely
small minority of ads originate from the same server as the page you are
looking at. The reason for this is that advertisers pay people to put
their ads on their websites, and these ads need to change frequently to
be effective. Hence these websites link to the advertiser's servers to
display the ads. Thus it's enough to blacklist the URLs pointing to the
ad-producing directories in the advertisers' servers.

  The advertisers can't change the URLs because it would break the millions
of websites which show those ads. Hence blacklisting is quite effective.

  Of course *new* ad servers and directories inside those servers pop up
all the time, but that's why the blacklists are updated.

-- 
                                                          - Warp

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