Re: [gentoo-user] clamav and spamassassin

[Grant]

>> I haven't set up any antivirus measures on my Gentoo systems so I
>> think I should.  Is clamav run as a scheduled filesystem scanner on
>> each system and as an email scanner on the mail server all that's
>> necessary?
>
>
> Nobody (as far as I know?) scans linux filesystems unless there's a legal
> requirement or the files might wind up on a Windows box.

Very cool.  I found out clamscan and avgfree scan the filesystem so I
thought I should set it up, but if it's not necessary I won't bother.
All of my mail users are on Gentoo so do I need to bother having
clamav scan my incoming mail?

>> I'm currently greylisting email to prevent spam from getting through.
>> It catches a lot, but more and more gets through.  I'm not using any
>> mailfilters now and If I set up a clamav mailfilter I think I may as
>> well set up a spamassassin mailfilter to take the place of
>> greylisting.  Is this the best guide for clamav and spamassassin:
>
>
> SpamAssassin shouldn't take the place of greylisting; they reject different
> stuff. Keep the greylisting unless the delays bother you, but use postscreen
> to do it (see below).

I just did some reading on postscreen but it doesn't sound like a
greylister.  Should I use postscreen in addition to postgrey, or are
they substitutes for each other?

>> http://www.gentoo.org/doc/en/mailfilter-guide.xml
>>
>> Could I run into any problems with clamav or spamassassin that might
>> make we wish I hadn't implemented them?
>
>
> Yeah. The first is false positives. The second, related problem is that
> you'll have to manage a quarantine unless you stick amavisd-new in front of
> the postfix queue.

Now that sounds like a hassle.  Greylisting leaves me with about 50/50
spam/legit mail and maybe incorporating postscreen I'll do even
better.  Deleting spam in my inbox might be easier than dealing with
false positives and managing a quarantine.

- Grant


> It's in that respect that the tutorial is outdated; otherwise, it looks good
> (I just skimmed it).
>
> There is great benefit to the before-queue setup: mail will never disappear.
> Senders either get a rejection, or the mail is delivered. With the
> after-queue setup, you can no longer reject or else you'll be
> backscattering. So, you either deliver the spam, or you quarantine it (very
> bad if it's a false positive).
>
> The downside is that you use more resources: one amavisd-new per connection.
> However, the addition of postscreen to postfix has largely ameliorated this.
> Since postscreen rejects most of the junk, amavis only gets started for
> smtpd sessions that are likely to succeed.
>
> The easiest way to migrate is through incremental improvement. We used to
> use a system like the one in that guide. I enabled postscreen over the
> course of a week, and retired postgrey, which we had been using for
> greylisting. Once that was working properly, I simply dropped the
> content_filter in favor of smtpd_proxy_filter to move amavis in front of the
> queue.