Best way to decrease DDoS with pf.

[Abdullah Ibn Hamad Al-Marri]

On 5/18/07, Kian Mohageri <kian.mohageri at gmail.com> wrote:
> On 5/18/07, Abdullah Ibn Hamad Al-Marri <almarrie at gmail.com> wrote:
> > On 5/18/07, Kian Mohageri <kian.mohageri at gmail.com> wrote:
> > > On 5/18/07, Abdullah Ibn Hamad Al-Marri <almarrie at gmail.com> wrote:
> > > > Thank you for the tip.
> > > >
> > > > Here what I'm using which fixed the issue.
> > > >
> > > > pass in on $ext_if proto tcp from any to $ext_if port $tcp_services
> > > > flags S/SA synproxy state
> > > > pass in on $ext_if proto tcp from any to $ext_if port $tcp_services \
> > > >         flags S/SA keep state \
> > > >         (max-src-conn 30, max-src-conn-rate 30/3, \
> > > >          overload <bruteforce> flush global)
> > > > pass out proto tcp to any keep state
> > > >
> > > > Comments?
> > >
> > > The first rule won't match anything (same criteria as second rule, and
> > > last match wins with pf).  On the third rule, use 'flags S/SA' unless
> > > you have a good reason not to.
> > >
> > > Kian
> > >
> >
> > I thought first rule will defeat syn flood.
> >
> >  Is the second rule going to do the same job as first rule and will
> > prevent syn flood?
>
> The rules are different obviously, but the criteria matches the same
> traffic.  Because PF will apply the last matching rule by default
> (unless 'quick' is used), your first rule will never be applied.  You
> could use synproxy state on the second rule, and remove the first
> entirely.
>
> > As for the third rule syntax, Should I make it like this?
> >
> > "pass out proto tcp to any flags S/SA keep state" and shall I add the
> > same for udp?
> >
> > "pass out proto udp to any flags S/SA keep state" ?
>
> If you only want to pass UDP and TCP, then you can do something like this:
>
> pass out proto tcp to any flags S/SA keep state
> pass out proto udp to any keep state
>
> Kian
>

Alright, can you give me synproxy in the first line entry? I tried to
add it, and I get error.

-- 
Regards,

-Abdullah Ibn Hamad Al-Marri
Arab Portal
http://www.WeArab.Net/