| 1 |
-----BEGIN PGP SIGNED MESSAGE----- |
| 2 |
Hash: SHA1 |
| 3 |
|
| 4 |
Stephen Clowater wrote: |
| 5 |
|
| 6 |
| You can not Block ICMP, it breaks tcp, its a "controll Message Prococol" |
| 7 |
| for a reason. If you block it, you can not send squelches, routes |
| 8 |
| unreachable, ect. Point being, block ICMP on your local box, you will |
| 9 |
| see a few odd problems, but nothing to devestaing. Block it on a pice of |
| 10 |
| networking hardware, you will $%@#$ up a network. |
| 11 |
|
| 12 |
Without attempting to make the thread any longer, the problem with the |
| 13 |
above logic is that it assumes that the 'firewall' system is not working |
| 14 |
with 'related' packets. You can drop all the ICMP traffic you want, the |
| 15 |
required ICMP packets will still get out (and in) so long as the |
| 16 |
'firewall' system keeps track of 'related sessions'. If an ICMP packet |
| 17 |
needs to get in and it's related to a current session, the firewall will |
| 18 |
let it in. If it's unrelated, it's dropped (of course). |
| 19 |
|
| 20 |
And that's the whole purpose of ip_conntrack. Any decent 'firewalling' |
| 21 |
script will implement this. Of course, I've been using Seawall (2.2) and |
| 22 |
Shorewall (2.4+) for years now without a glitch on personal and |
| 23 |
corporate/production 'firewalls' and routers. |
| 24 |
|
| 25 |
Try: |
| 26 |
"Keeping track of packets: The state match" |
| 27 |
http://www.linux-mag.com/2000-01/bestdefense_03.html |
| 28 |
(part of) |
| 29 |
"BEST DEFENSE: Network Security With Linux 2.4" |
| 30 |
http://www.linux-mag.com/2000-01/bestdefense_01.html |
| 31 |
|
| 32 |
modprobe ip_conntrack |
| 33 |
iptables -I INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT |
| 34 |
|
| 35 |
Regards, |
| 36 |
Paul <snafu@××××××××××××.org> |
| 37 |
|
| 38 |
BLOG: http://forkbomb.dhs.org/bs/ |
| 39 |
GPG Key: http://forkbomb.dhs.org/bs/snafu.asc |
| 40 |
- --- |
| 41 |
Life would be so much easier if we could just look at the source code. |
| 42 |
~ -- Dave Olson |
| 43 |
-----BEGIN PGP SIGNATURE----- |
| 44 |
Version: GnuPG v1.2.4 (GNU/Linux) |
| 45 |
|
| 46 |
iD8DBQFAAVrtNQvzkbg+TpsRAutAAJ40Bk+FwG5UZoXW95d8SXmnHZ/ljACeNzWE |
| 47 |
usrHkixM2uPsL1D5Zbie0nE= |
| 48 |
=HlVb |
| 49 |
-----END PGP SIGNATURE----- |
| 50 |
|
| 51 |
-- |
| 52 |
gentoo-security@g.o mailing list |
Archives