I just, maybe, figured out why I have been having problems with my CentOS DNS server with BIND 9.11.4. Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.194.4#11205 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.216.196#64956 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 64.68.114.141#39466 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 209.197.198.45#13280 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.202.117#41955 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 62.109.204.22#4406 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:49 onlo named[6155]: client @0xa9420720 64.68.104.9#38518 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:50 onlo named[6155]: client @0xaa882dc8 114.29.202.117#9584 (.): view external: query (cache) './A/IN' denied grep -c denied messages 46038 And that is since Jul 31 3am. Anyone have recommendations on how to stop this? thanks
Maybe try Fail2Ban on your server? -----Original Message----- From: CentOS <centos-bounces at centos.org> On Behalf Of Robert Moskowitz Sent: Tuesday, August 2, 2022 2:03 PM To: CentOS mailing list <centos at centos.org> Subject: [External] [CentOS] BIND server getting DDOS I just, maybe, figured out why I have been having problems with my CentOS DNS server with BIND 9.11.4. Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.194.4#11205 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.216.196#64956 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 64.68.114.141#39466 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 209.197.198.45#13280 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.202.117#41955 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 62.109.204.22#4406 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:49 onlo named[6155]: client @0xa9420720 64.68.104.9#38518 (.): view external: query (cache) './A/IN' denied Aug? 2 15:47:50 onlo named[6155]: client @0xaa882dc8 114.29.202.117#9584 (.): view external: query (cache) './A/IN' denied grep -c denied messages 46038 And that is since Jul 31 3am. Anyone have recommendations on how to stop this? thanks _______________________________________________ CentOS mailing list CentOS at centos.org https://lists.centos.org/mailman/listinfo/centos
On 8/2/22 14:03, Robert Moskowitz wrote:> I just, maybe, figured out why I have been having problems with my > CentOS DNS server with BIND 9.11.4.Can you tell us more about what problem you've been having?> Aug 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.194.4#11205 > (.): view external: query (cache) './A/IN' denied > > grep -c denied messages > 46038 > > And that is since Jul 31 3am.If I'm not mistaken, your system is averaging one query denied every 4.6 seconds.? That's not a large volume, as an average. Probably not a DDOS... A DNS server connected to the internet is very likely to get occasional q ueries.> Anyone have recommendations on how to stop this?If this server is the authoritative server for domains: completely turn off recursive support.? Authoritative servers should serve their authoritative domains, only. If this server offers recursive queries to your local network, use its firewall to allow traffic from the networks that are allowed to make queries, and drop all other traffic. Disable connection tracking for port 53 in your firewall. https://kb.isc.org/docs/bind-best-practices-recursive https://kb.isc.org/docs/aa-01183
On Tue, 2 Aug 2022, Robert Moskowitz wrote:>I just, maybe, figured out why I have been having problems with my CentOS DNS >server with BIND 9.11.4. > > Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.194.4#11205 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.216.196#64956 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 64.68.114.141#39466 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 209.197.198.45#13280 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 114.29.202.117#41955 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:19 onlo named[6155]: client @0xaa3cad80 62.109.204.22#4406 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:49 onlo named[6155]: client @0xa9420720 64.68.104.9#38518 (.): view external: query (cache) './A/IN' denied > Aug? 2 15:47:50 onlo named[6155]: client @0xaa882dc8 114.29.202.117#9584 (.): view external: query (cache) './A/IN' deniedUsually that's someone hoping to use you in a reflection attack, which is successful since UDP can be forged but it hasn't got the volume it might if you answered differently (with a referral). Sometimes it is a policy denial attack, hoping you will block the apparent source thus denying it service. The only way to stop it is for all others to employ BCP 38 which will likely never happen, or for you to stop allowing outside use of your nameserver which means having someone else handle DNS for you (which just seems to stop it, from your perspective). It shouldn't cause problems unless your server is vastly underpowered. What problems are you experiencing? /mark