norgaard at locolomo.org
Tue Jun 22 19:36:34 UTC 2010
On 21/06/10 20.06, pete wright wrote:
>> On Jun 21, 2010, at 10:28 AM, Jean-Paul Natola wrote:
>>> I'm particuclary trying to implement some type of rate control as we are getting hammered by spam.
> I'd humbly suggest pf + spamd if you are concerned specifically about
> stopping spam, both are supported by freebsd and i have had great
> success using these tools to combat spam.
spamd does not stop spam. It is intented to increase the cost of sending
spam at little cost to your server by keeping the spammer busy trying.
If you're concerned with blocking spam from a limited set of known
sources, then you can create block lists in your firewall. If you know
that you will not receive legitimate mails from certain countries, you
can block their assigned IP ranges.
If you're trying to block large number of unknown sources, then I
suggest subscribing to spamhaus' lists and configure your server to
adhere strictly to the protocols.
You may wish to subscribe to lists of dynamic ip-ranges. These are often
considered spam sources hosting a large number of bot-nets However, you
may also block mail from legitimate servers run by people who like to
run their own home server - such as FreeBSD users.
There is only limited benefit of some kind of rate control and I believe
that such controls must be implemented in your mail server. Implementing
rate control mail also delay legitimate mail, and depending on how you
do it, spammers may even cause a DOS against your server.
Anyway, to avoid spammers eating up server resources, check your server
1. ensure that the spam decision is reached as fast as possible
2. consider early whitelisting of the most common legitimate mail sources
3. DNS block lists should be last as they add additional delay, possibly
you can configure a local dns cache to shorten delay
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