From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Gale <mgale@utilitran.com>
Subject: Re: Protecting against DoS
Date: Tue, 9 Dec 2003 09:40:47 -0700
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Hello,

	Can you provide more detail on the type of traffic that caused the DOS -- =
this may help people in the list with suggestions on how to block it :)

Michael.



On Tue, 9 Dec 2003 18:28:20 +0200
Pasi K=E4rkk=E4inen <pasik@iki.fi> wrote:

> On Tue, Dec 09, 2003 at 09:02:21AM -0700, Michael Gale wrote:
> >=20
> > Hello,
> >=20
> > 	First make sure you are using tcpsyn_cookies:
> >=20
> > echo 1 > /proc/sys/net/ipv4/tcp_syncookies -- if you have not compiled =
it into the kernel.=20
> > This will help prevent DOS by assigning each incoming syn packet a cook=
ie instead of a actually=20
> > connection state. A connection state will be created once the three way=
 hand shake is completed.
> >=20
> > Second -- you should be dropping all packets on all interfaces and then=
 only allow connections=20
> > you have to pass.
> >=20
>=20
> Yes.. I'm already doing both of these things. I was thinking of doing some
> extra in addition of these.. Sorry I didn't mention about these already.
>=20
> There are always some connections allowed that can be used to fill up the
> state table..
>=20
> Thanks anyway!
>=20
> > Michael.
> >=20
>=20
> -- Pasi K=E4rkk=E4inen
>       =20
>                                    ^
>                                 .     .
>                                  Linux
>                               /    -    \
>                              Choice.of.the
>                            .Next.Generation.
>=20


--=20
Michael Gale
Network Administrator
Utilitran Corporation