Re: Block outbound host to specific port(s) using Masq./NAT?

[Georgi Alexandrov <tehlists@hotpop.com>]

If you're getting into "greping" packets payload for different 
apps/services, you can try layer 7 filtering - 
http://l7-filter.sourceforge.net/

regards,
Georgi Alexandrov


Jerry2A wrote:

>Hello - this is probably a dumb question....I'm using iptables for my
>home network (DSL) and I have masquerading, some port forwarding,
>etc., etc., and everything works great...EXCEPT....I have a situation
>where I occaisionally want to block outbound traffic from a certain
>host inside to a certain destination IP and/or port.  For example, I'd
>like to block one host from within my network from using Instant
>Messenger but still allow web surfing.  I've been able to dynamically
>block ALL outbound access to the internet but I'm unable to restrict
>access to certain destination ports.
>
>So this works:
>iptables -A INPUT -s 10.1.1.10 -j DROP
>iptables -A OUTPUT -d 10.1.1.10 -j DROP
>iptables -A FORWARD -d 10.1.1.10 -j DROP
>
>And I thought I could do something like this:
>iptables -A OUTPUT -s 10.1.1.10 -p tcp -m tcp --dport 5190 -j DROP
>iptables -A FORWARD -d 10.1.1.10 -p tcp -m tcp --dport 5190 -j DROP
>....but it has no effect.
>
>I've tried different combinations of "-d and -s" and "--dport and
>--sport" just to see if I was doing something backwards....no dice.  I
>was wondering if I needed to set up some kind of pre or post routing
>because of the masquerading?
>
>Any help would be appreciated.
>
>Thanks!
>
>Jerry A.
>
>
>  
>