On Jan 29, 2008, at 9:43 AM, Jim Popovitch wrote:
On Jan 29, 2008 12:58 AM, Patrick W. Gilmore <[EMAIL PROTECTED]>
wrote:
A general purpose host or firewall is NOTHING like a mail server.
There is no race condition in a mail server, because the server
simply
waits until the DNS query is returned. No user is watching the mail
queue, if mail is delayed by 1/10 of a second, or even many seconds,
nothing happens.
Now magine every web page you visit is suddenly paused by 100ms, or
1000ms, or multiple seconds? Imagine that times 100s or 1000s of
users. Imagine what your call center would look like the day after
you implemented it. (Hint: Something like a smoking crater.)
There might be ways around this (e.g. zone transfer / bulk load), but
it is still not a good idea.
Of course I could be wrong. You shouldn't trust me on this, you
should try it in production. Let us know how it works out.
Andrew, IIUC, suggested that the default would be to allow while the
check was performed.
I read that, but discounted it. There has been more than one single-
packet compromise in the past. Not really a good idea to let packets
through for a while, _then_ decide to stop them. Kinda closing the
bard door after yada yada yada.
Perhaps combine the two? Have a stateful firewall which also checks
DNSBLs? I can see why that would be attractive to someone, but still
not a good idea. Not to mention no DNSBL operator would let any
reasonably sized network query them for every new source address - the
load would squash the name servers.
As I mentioned, zone transfer the DNSBL and check against that might
add a modicum of usefulness, but still has lots of bad side effects.
Then again, what do I know? Please implement this in production and
show me I'm wrong. I smell a huge business opportunity if you can get
it to work!
--
TTFN,
patrick
