Re: Deny MX queries for dynamic IP pools
Dear All, Thank you for the valuable comments to this post. Sincerely, Wael On 2/2/10 4:26 AM, Sven Eschenberg s...@whgl.uni-frankfurt.de wrote: There have been quite some posts since my first answer to Wael. I just wanted to rephrase some stuff etc. On Tue, February 2, 2010 00:43, Peter Dambier wrote: Noel Butler wrote: Firstly, I feel this really belongs on mailops not bind list :) secondly... On Mon, 2010-02-01 at 00:00 +0300, Wael Shaheen wrote: Blocking port 25 is much worse IMHO because it forces users out of the service, by restricting their ability to use their own mail servers that can be hosted externally. I believe good mail administrators will force SMTPS Blocking DNS belongs here. I don't think blocking DNS is a good idea. You are blocking access to zones using strictly internal DNS that is not published but only AXFRed and you are blocking alternative DNS. In germany alternative DNS is a must as many ISPs are stumbling over their own feet when implementing or testing censoring. Maybe some of the DNS blackouts here have been DNSSEC as well. Dear fellow pirate, the local situation in Germany might not be relevant here for Wael, esp. if he works at some ISP and there are no plans to manipulate DNS otherwise. Yet I do agree as I stated in my first post, I don't think, filtering/blocking/modifying requests in any way whatsoever is an appropriate approach to a non-technical problem (as I said before). Let it be DNS or directly blocking port 25. Here we do block port 25 within our own network - to put it in short, if a customer thinks this policiy is appropriate, let the customer deploy it, don't do the customers job and don't give the customer options of taking legal actions because you break the customers setups. Oh, how about DNSSEC? How do you handle signatures? And you are breaking dnsbl because dnsbl is DNS at an alternative address. So some of your clients might accidently drop all mail as spam and it takes long to find such a bug if somebody else does maintain the mailer. That is indeed true, I did forget about those in my first post. That brings me back to my first argument: Don'T use technical methods for a non technical problem, there many good reasons not to do this. The bigger question is why are you not blocking, suspending, or terminating the accounts of those who you know are spamming, be it deliberate, or not (as the end result is the same) Cheers Cheers Peter and Karin -- Peter and Karin Dambier Cesidian Root - Radice Cesidiana Rimbacher Strasse 16 D-69509 Moerlenbach-Bonsweiher +49(6209)795-816 (Telekom) +49(6252)750-308 (VoIP: sipgate.de) mail: pe...@peter-dambier.de http://www.peter-dambier.de/ http://iason.site.voila.fr/ https://sourceforge.net/projects/iason/ ULA= fd80:4ce1:c66a::/48 ___ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users Now Andrew said it pretty catchy already, let me rephrase my thoughts: Why do you want to use some technical approach like filtering/blocking, to solve a social problem. You as an ISP should have an agreement/contract with your customers. It's the right place, to enforce, that customers take action against spam. If they do not comply, willingly or due to incompetence, it is at your hand, to disconnect them and terminate the agreement, if necessary. And of course you can take additional legal action when needed. This is just plain simple social engineering and imho the only valid solution. Wael, you said something about mail hosts on dynamic IP Pools being 'illegal' - If it is under your jurisdictional system, well, you already had the answer/solution, to all your problems, if not, work out an appropriate contract. Regards -Sven ___ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users ___ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
Deny MX queries for dynamic IP pools
Dear DNS Experts, This post is intended for discussion. The ISP I work for has HUGE dynamic IP pools that are full of spammers (of course). This huge volume of spam is actually influencing the decision for some of the international provider¹s whether to give us links or not let alone the bad reputation and RBLs listing etc... As a solution the routing team was thinking to block port 25 for outgoing as some ISPs do. However, I do not see this to be a valid solution for many reasons such as clients that have email servers outside, or if decided to be redirected to spam filters then that will just cost the company too much. Luckily we have two set of DNS server farms; one that is serving static IP users and one that is dedicated only for dynamic IP users. The idea I have proposed is to deny these dynamic users from performing MX queries. So instead of blocking port 25 we can redirect the DNS port to the DNS farm that is dedicated for dynamic users, that will guarantee that no standard DNS port forwarded queries are going to external servers. Then we will block the MX and root queries for those dynamic clients. That will prevent them from using a locally installed DNS service on their machines or query MX records for targets they want to send spam to. Of course there will still be some challenges like if some spammers know the A record of the mail server they want to connect to or if they used the IP address of the targeted mail server also if they used open dns that works on non-standard ports, but then again I believe these users will stand out and will be identified more easily. I would appreciate any comments you may have. Sincerely, Wael ___ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
Re: Deny MX queries for dynamic IP pools
Hi, On 1/31/10 5:17 PM, Sven Eschenberg s...@whgl.uni-frankfurt.de wrote: Dear Wael, In what way is blocking Port 25 any worse than blocking MX/root queries for clients? Both solutions neglect the fact, that spam is not a technical problem. This spam issue is major for DSPs and large ISPs. Their reputation is key in acquiring connections from some major international providers. This brings the issue to a very high priority for connectivity is the most important part. Blocking port 25 is much worse IMHO because it forces users out of the service, by restricting their ability to use their own mail servers that can be hosted externally. I believe good mail administrators will force SMTPS which uses a different port but then again a lot wont, and hence blocking SMTP service will deny all of these users from accessing their email servers and most of these users are not technically educated enough to find a workaround. On the other hand denying the dynamic user MX/root queries will affect users that have installed mail servers on their systems or otherwise infected and both of these scenarios are illegal for dynamically assigned IPs. Some ISPs think it is a good idea to forward you to a search web page, when you mispell some URL, this is done via DNS. Obviously, if the customer dislikes this, the customer will (and can) use his/her own recursor, We do not redirect users if they misspelled their destinations and we do not manipulate DNS replies in any way. Some users may choose to use their own installed DNS service, but then again if your service provider has a stable DNS service and a good and stable internet connection then would that overcome this disadvantage? At the end I think that something has to be sacrificed. Sincerely, Wael Shaheen ___ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
Re: Deny MX queries for dynamic IP pools
Hi, On 1/31/10 5:28 PM, Sten Carlsen st...@s-carlsen.dk wrote: To me this seems to be a firewall/routing issue. If you know for sure that some IP is sending spam, if you can not stop them, then at least you can block their outgoing access to port 25. Most of the RBLs list dynamic IP addresses for they should not be sending emails whatsoever in most cases. Identifying the the origin of the spam in huge networks with thousands of compromised machines is not an easy task and blocking the port 25 based on that network analysis will produce false positives for these are dynamically assigned IP addresses and will change with every time the user connects. Alternatively and maybe better arrange for a proxy server to do filtering and discard spam. The proxy solution is actually used many places and works reasonably well also for non-spammers. The email proxy can work in many places but I am not sure it would in a DSP, or a big ISP. If you want to cope with the email volume that is being generated by hundreds of thousands of clients then you will need to build a monster solution. Not only that, you also may cause your users legitimate emails to be rejected or flagged as SPAM for they will be sent from a destination other than their email server. Regards, Wael ___ bind-users mailing list bind-users@lists.isc.org https://lists.isc.org/mailman/listinfo/bind-users
