I'd say that it is not a wise thing to do, but it is up to you.
Inside this /8 block there are a lot allocation to important networks
in our region.
There is also, users that send spam from these IPs, but I see this all
the time from IP blocks of all over the world.
It is an effective solution in my specific application, with my set of
users. I have a 100% hit rate with no false positives. I am not
suggesting other folks do the same unless their requirements are also
the same. I certainly wouldn't do this at my day job as
postmaster@sony.com, for example.
According to some statistics USA is one of the top in the list of
spammers.
Do you filter all American blocks in your network? I guess not. You
wisely filter only some, like this 69.6.0.0/18.
I filter the blocks that I see a 1:0 spam to ham ratio from, wherever
they are located. I also try to aggregate where I can. The LACNIC
blocks were a convenient place to do so.
Do you filter all Asia blocks? I guess not...
I certainly do filter abuseive asian networks, except for networks
that my users need connectivity to, or networks that I have not seen
abuse from:
http://mrtg.snark.net/blacklist.cgi
I think you'll see that there's no region singled out there. You might
also be forgetting that the reason I singled out the LACNIC blocks, is
that they are the third largest source of unwanted SMTP traffic I see.
I'm sorry if my actions have offended you, because there really is
nothing personal going on here, just pragmatism and a desire to
prevent as much spam as possible from reaching my users.
Matt Ghali
speaking as postmaster@snark.net only
--matt@snark.net------------------------------------------<darwin><
Flowers on the razor wire/I know you're here/We are few/And far
between/I was thinking about her skin/Love is a many splintered
thing/Don't be afraid now/Just walk on in. #include <disclaim.h>