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The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

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Re: [vox-tech] more fires to put out
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Re: [vox-tech] more fires to put out


  • Subject: Re: [vox-tech] more fires to put out
  • From: Doug Barbieri <doug@trug.MAPScom>
  • Date: Sat, 12 May 2001 10:04:19 -0700
  • References: Pine.GSO.4.33.0105120359270.28776-100000@logan.ucdavis.edu

I found this tool online which was invaluable in helping me configure my
firewall. I wanted full control of which ports are opened but at the time
really didn't understand ipchains. Check it out at:

http://www.linux-firewall-tools.com/linux/

Click the link "Firewall Design Tool." This site will then take you
through a series of steps which allow you to setup a firewall to your
specifications. It then gives you a shell script output which is really
handy.

 On Sat, 12 May 2001, Gabriel Rosa wrote:

> hey all,
> 
> this is a bit shaky ground for me, so i'll ask at the risk of sounding
> ignorant. anyway, so a couple of hours ago portsentry caught someone doing a
> udp scan on my system, so just to be sure, i can a udp scan on my system from
> outside my network.
> 
> well, it turns out all my ports are open (and yes, it's my fault).
> the problem is that I didn't want to specify rules for every possible udp
> service I may use, so I just put a allow all in there, not really thinking
> about it. (i figured only the ports with services would be open).
> 
> from what i can tell, a lot _more_ ports are open. So i'm getting paranoid.
> 
> my questions are:
> 
> 1. is there a way to only allow return packets in? iirc, with tcp you set the
> syn flag to specify that the packet is a return packet, and ipchains has an
> option for that. is there a similar method for udp, or do I have to spend some
> time figuring out which ports i like and which i don't (maybe i can simplify
> by filtering out hosts?) ?
> 
> 2. is udp that big of a deal? do i really care if my udp ports are open? some
> important services (for me) like dns depend on udp (like dns)
> 
> 3. how do people normally deal with this?
> 
> any help would be appreciated
> thanks
> 
> -Gabe
> 
> 

-- 
R. Douglas Barbieri
doug@trug.com


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