You might want to refer to this? https://closedresolver.korlabs.io/ https://mkorczynski.com/PAM2020Korczynski.pdf
The source IP address may be disguised as a permission range. I call this kind of resolvers as "hidden open resolver". https://www.e-ontap.com/misc/ieice2023oki/#(3) ... (Japanese) On Tue, 25 Mar 2025 09:36:54 +0000 sir izake via Unbound-users <unbound-users@lists.nlnetlabs.nl> wrote: > Unfortunately, the changes didn't yield much results. The flood attack > happened again but at a different time. > > Any more suggestions? > > Regards, > izake > > On Mon, Mar 24, 2025 at 12:18 PM sir izake <siriz...@gmail.com> wrote: > > > thank you all > > > > "unbound-control get_option access-control" shows a list of IP blocks I > > have allowed/denied. > > > > I have also done the explicit deny and recommended config hardening. > > > > I will monitor and see if the issue reoccurs. > > > > Thank you > > izake > > > > > > > > > > On Mon, Mar 24, 2025 at 10:48 AM <unbound-users-requ...@lists.nlnetlabs.nl> > > wrote: > > > >> Send Unbound-users mailing list submissions to > >> unbound-users@lists.nlnetlabs.nl > >> > >> To subscribe or unsubscribe via the World Wide Web, visit > >> https://lists.nlnetlabs.nl/mailman/listinfo/unbound-users > >> or, via email, send a message with subject or body 'help' to > >> unbound-users-requ...@lists.nlnetlabs.nl > >> > >> You can reach the person managing the list at > >> unbound-users-ow...@lists.nlnetlabs.nl > >> > >> When replying, please edit your Subject line so it is more specific > >> than "Re: Contents of Unbound-users digest..." > >> > >> > >> Today's Topics: > >> > >> 1. Unbound dns resolver involved in DNS Amplification attack > >> (sir izake) > >> 2. Re: Unbound dns resolver involved in DNS Amplification attack > >> (Yuri) > >> 3. Re: Unbound dns resolver involved in DNS Amplification attack > >> (Cristiano Deana) > >> 4. Re: Unbound dns resolver involved in DNS Amplification attack > >> (Yuri) > >> > >> > >> ---------------------------------------------------------------------- > >> > >> Message: 1 > >> Date: Mon, 24 Mar 2025 10:18:38 +0000 > >> From: sir izake <siriz...@gmail.com> > >> To: unbound-users@lists.nlnetlabs.nl > >> Subject: Unbound dns resolver involved in DNS Amplification attack > >> Message-ID: > >> < > >> caacq5hcu_6i_hqapfuaqwezhee_wd9mqdauo4njjigh8cmz...@mail.gmail.com> > >> Content-Type: text/plain; charset="utf-8" > >> > >> Hi > >> > >> I run an unbound dns cache resolver (version 1.22.0) on a freebsd 14.2 > >> server. It is configured to only respond to queries from the local host > >> and > >> my network IP block. > >> > >> Recently, I detected my server was involved in a DNS amplification attack. > >> By default unbound doesn't respond to any query outside those allowed in > >> the access list in the config file. How do I uncover the source IPs > >> involved and potentially block them. > >> > >> Are there other options I need to enable to prevent further amplification > >> attacks? > >> > >> I have checked the server and don't see any suspicious process running. > >> > >> Your support and advice is greatly appreciated. > >> > >> Regards > >> izake > >> -------------- next part -------------- > >> An HTML attachment was scrubbed... > >> URL: < > >> http://lists.nlnetlabs.nl/pipermail/unbound-users/attachments/20250324/a68a1439/attachment-0001.htm > >> > > >> > >> ------------------------------ > >> > >> Message: 2 > >> Date: Mon, 24 Mar 2025 15:32:42 +0500 > >> From: Yuri <yvoi...@gmail.com> > >> To: unbound-users@lists.nlnetlabs.nl > >> Subject: Re: Unbound dns resolver involved in DNS Amplification attack > >> Message-ID: <c957df77-cc37-4d5a-9dc0-8f3e78f0c...@gmail.com> > >> Content-Type: text/plain; charset="utf-8"; Format="flowed" > >> > >> To begin, restrict access from outside using standard Unbound > >> configuration (example from one of my setups): > >> > >> ??? access-control: 0.0.0.0/0 refuse > >> ??? access-control: 127.0.0.0/8 allow_snoop > >> ??? access-control: 192.168.0.0/16 allow_snoop > >> ??? access-control: 172.16.0.0/12 allow_snoop > >> ??? access-control: ::0/0 refuse > >> ??? access-control: ::1 allow > >> ??? access-control: ::ffff:127.0.0.1 allow > >> > >> Additionally, cut off external access with a server firewall and/or on > >> the border. And finally, check the internal network to see if it is > >> trooped. > >> > >> 24.03.2025 15:18, sir izake via Unbound-users ?????: > >> > Hi > >> > > >> > I run an unbound dns cache resolver (version 1.22.0) on a freebsd 14.2 > >> > server. It is configured to only respond to queries from the local > >> > host and my network IP block. > >> > > >> > Recently, I detected my server was involved in a DNS amplification > >> > attack.? By default unbound doesn't respond to any query outside those > >> > allowed in the access list in the config file. How do I uncover the > >> > source IPs involved and potentially block them. > >> > > >> > Are there other options I need to enable to prevent further > >> > amplification attacks? > >> > > >> > I have checked the server and don't?see any suspicious process running. > >> > > >> > Your support and advice is greatly appreciated. > >> > > >> > Regards > >> > izake > >> -------------- next part -------------- > >> An HTML attachment was scrubbed... > >> URL: < > >> http://lists.nlnetlabs.nl/pipermail/unbound-users/attachments/20250324/45920e7f/attachment-0001.htm > >> > > >> > >> ------------------------------ > >> > >> Message: 3 > >> Date: Mon, 24 Mar 2025 11:33:26 +0100 > >> From: Cristiano Deana <cristiano.de...@megaweb.it> > >> To: unbound-users@lists.nlnetlabs.nl > >> Subject: Re: Unbound dns resolver involved in DNS Amplification attack > >> Message-ID: <b25581c2-8068-440a-b590-f0e3ad612...@megaweb.it> > >> Content-Type: text/plain; charset=UTF-8; format=flowed > >> > >> Il 24/03/2025 11:18, sir izake via Unbound-users ha scritto: > >> > >> Hi, > >> > >> > I run an unbound dns cache resolver (version 1.22.0) on a freebsd 14.2 > >> > server. It is configured to only respond to queries from the local host > >> > and my network IP block. > >> > >> what do you get with `unbound-control get_option access-control'? > >> > >> > Recently, I detected my server was involved in a DNS amplification > >> > attack.? By default unbound doesn't respond to any query outside those > >> > allowed in the access list in the config file. How do I uncover the > >> > source IPs involved and potentially block them. > >> > > >> > Are there other options I need to enable to prevent further > >> > amplification attacks? > >> > > >> > I have checked the server and don't?see any suspicious process running. > >> > > >> > Your support and advice is greatly appreciated. > >> > > >> > Regards > >> > izake > >> > >> -- > >> > >> ############################### > >> # Cristiano Deana # > >> # # > >> # Senior Network Engineer # > >> # Digital Response Team # > >> # CittaStudi S.p.a. # > >> # off. +39 015 855 1172 # > >> # cell +39 328 310 6392 # > >> ############################### > >> > >> > >> > >> ------------------------------ > >> > >> Message: 4 > >> Date: Mon, 24 Mar 2025 15:48:03 +0500 > >> From: Yuri <yvoi...@gmail.com> > >> To: unbound-users@lists.nlnetlabs.nl > >> Subject: Re: Unbound dns resolver involved in DNS Amplification attack > >> Message-ID: <55c63a28-03e3-4bbf-9b58-80b5786c9...@gmail.com> > >> Content-Type: text/plain; charset="utf-8"; Format="flowed" > >> > >> Ah, I was inattentive. It seems to me that a consistent set of actions > >> is needed here, as in the case of an incident. Listening to traffic - in > >> order to catch illegitimate traffic and try to determine its source. > >> Scanning the external access point for open ports. Checking the firewall > >> and routing settings. And - yes, of course, it is worth starting with > >> checking the config and its hardening. > >> > >> 24.03.2025 15:33, Cristiano Deana via Unbound-users ?????: > >> > Il 24/03/2025 11:18, sir izake via Unbound-users ha scritto: > >> > > >> > Hi, > >> > > >> >> I run an unbound dns cache resolver (version 1.22.0) on a freebsd > >> >> 14.2 server. It is configured to only respond to queries from the > >> >> local host and my network IP block. > >> > > >> > what do you get with `unbound-control get_option access-control'? > >> > > >> >> Recently, I detected my server was involved in a DNS amplification > >> >> attack.? By default unbound doesn't respond to any query outside > >> >> those allowed in the access list in the config file. How do I uncover > >> >> the source IPs involved and potentially block them. > >> >> > >> >> Are there other options I need to enable to prevent further > >> >> amplification attacks? > >> >> > >> >> I have checked the server and don't?see any suspicious process running. > >> >> > >> >> Your support and advice is greatly appreciated. > >> >> > >> >> Regards > >> >> izake > >> > > >> -------------- next part -------------- > >> An HTML attachment was scrubbed... > >> URL: < > >> http://lists.nlnetlabs.nl/pipermail/unbound-users/attachments/20250324/b2d8cd29/attachment.htm > >> > > >> > >> ------------------------------ > >> > >> Subject: Digest Footer > >> > >> _______________________________________________ > >> Unbound-users mailing list > >> Unbound-users@lists.nlnetlabs.nl > >> https://lists.nlnetlabs.nl/mailman/listinfo/unbound-users > >> > >> > >> ------------------------------ > >> > >> End of Unbound-users Digest, Vol 63, Issue 9 > >> ******************************************** > >> > > -- 鈴木常彦 / (株) リフレクション
