From: Pascal Hambourg <pascal.mail@plouf.fr.eu.org>
To: netfilter@lists.netfilter.org
Subject: Re: Preventing port scanning using iptables ?
Date: Sun, 06 Aug 2006 13:15:00 +0200 [thread overview]
Message-ID: <44D5CF34.4060406@plouf.fr.eu.org> (raw)
In-Reply-To: <6c6b5e1c0daf49cbc42b7ecc329cc3e7@former03.de>
Hello,
former03 | Baltasar Cevc a écrit :
>
> Just for the record: there is a side effect the dropping behaviour.
> While not exposing whether the port is open or closed, show some
> scanners will conclude that there is a filter. If you want the scanner
> to think the ports are closed, you could issue send back a port
> unreachable packet (-j REJECT --reject-with icmp-port-unreachable)
This works only against UDP scans or basic TCP scans using the "connect"
method. A more advanced TCP scan will detect a packet filter when
receiving an ICMP port unreachable instead of a TCP RST which is the
normal reply for a closed TCP port. A TCP port is properly firewalled
using "-j REJECT --reject-with tcp-reset".
next prev parent reply other threads:[~2006-08-06 11:15 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-05 6:23 Preventing port scanning using iptables ? Elvir Kuric
2006-08-05 7:14 ` Ruprecht Helms
2006-08-05 8:00 ` Elvir Kuric
2006-08-05 13:41 ` Sietse van Zanen
2006-08-06 9:26 ` former03 | Baltasar Cevc
2006-08-06 11:15 ` Pascal Hambourg [this message]
2006-08-09 2:29 ` Michael Rash
2006-08-09 8:47 ` Marc Haber
2006-08-10 1:28 ` R. DuFresne
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=44D5CF34.4060406@plouf.fr.eu.org \
--to=pascal.mail@plouf.fr.eu.org \
--cc=netfilter@lists.netfilter.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.