Hi Everyone,
We rent a CentOS 7 VM from GoDaddy. We received a warning about excessive cpu usage, and a threat to cancel our service. We tracked it down to Apache and someone hammering our web server.
The offending host is 59.64.129.175. To err on the side of caution we attempted to block the entire netblock. According to whois data, that's 59.64.128.0-59.64.159.255.
iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROP
After reboot cpu usage is still high and access_log still shows useless requests from the host:
59.64.129.175 - - [19/Apr/2020:08:53:53 -0400] "GET /w/index.php?title=Special:WhatLinksHere&limit=50& printable=yes HTTP/1.1" 301 311
I seem to be missing something. That's not surprising since I am not a server administrator.
How do I filter the unwanted traffic from the netblock?
Thanks in advance.
On 19/04/2020 14:58, Jeffrey Walton wrote:
Hi Jeffrey,
The offending host is 59.64.129.175. To err on the side of caution we attempted to block the entire netblock. According to whois data, that's 59.64.128.0-59.64.159.255.
iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROPAfter reboot cpu usage is still high and access_log still shows useless requests from the host:
Did you actually arrange for your iptables rule to be reinstated at boot?
If you just configure a rule as above, but don't save it, it will disappear ar reboot.
Regards, Anand
On Sun, Apr 19, 2020 at 9:26 AM Anand Buddhdev anandb@ripe.net wrote:
On 19/04/2020 14:58, Jeffrey Walton wrote:
Hi Jeffrey,
The offending host is 59.64.129.175. To err on the side of caution we attempted to block the entire netblock. According to whois data, that's 59.64.128.0-59.64.159.255.
iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROPAfter reboot cpu usage is still high and access_log still shows useless requests from the host:
Did you actually arrange for your iptables rule to be reinstated at boot?
If you just configure a rule as above, but don't save it, it will disappear ar reboot.
Ugh, thanks. I did not realize the changes were only temporary.
What is the recommended way to permanently add a ban rule?
Thanks again.
Thought it might also be helpful to confirm that firewalld is not interfering in any way.
what is the output of ~$# systemctl status firewalld
On Sun, Apr 19, 2020 at 9:30 AM Jeffrey Walton noloader@gmail.com wrote:
On Sun, Apr 19, 2020 at 9:26 AM Anand Buddhdev anandb@ripe.net wrote:
On 19/04/2020 14:58, Jeffrey Walton wrote:
Hi Jeffrey,
The offending host is 59.64.129.175. To err on the side of caution we attempted to block the entire netblock. According to whois data, that's 59.64.128.0-59.64.159.255.
iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROPAfter reboot cpu usage is still high and access_log still shows useless requests from the host:
Did you actually arrange for your iptables rule to be reinstated at boot?
If you just configure a rule as above, but don't save it, it will disappear ar reboot.
Ugh, thanks. I did not realize the changes were only temporary.
What is the recommended way to permanently add a ban rule?
Thanks again. _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
On Sun, Apr 19, 2020 at 9:40 AM Mike 1100100@gmail.com wrote:
Thought it might also be helpful to confirm that firewalld is not interfering in any way.
what is the output of ~$# systemctl status firewalld
Thanks Mike.
# systemctl status firewalld Unit firewalld.service could not be found.
Jeff
The way I start the firewall is as follows:
systemctl enable firewalld systemctl start firewalld systemctl status firewalld
Regards, Mark Woolfson MW Consultancy Ltd Leeds LS18 4LY United Kingdom Tel: +44 113 259 1204 Mob: +44 786 065 2778 -----Original Message----- From: Jeffrey Walton Sent: Sunday, April 19, 2020 2:44 PM To: CentOS mailing list Subject: Re: [CentOS] Netfilter fails to filter traffic from a netblock?
On Sun, Apr 19, 2020 at 9:40 AM Mike 1100100@gmail.com wrote:
Thought it might also be helpful to confirm that firewalld is not interfering in any way.
what is the output of ~$# systemctl status firewalld
Thanks Mike.
# systemctl status firewalld Unit firewalld.service could not be found.
Jeff _______________________________________________ CentOS mailing list CentOS@centos.org https://lists.centos.org/mailman/listinfo/centos
On 19/04/2020 15:30, Jeffrey Walton wrote:
Ugh, thanks. I did not realize the changes were only temporary.
What is the recommended way to permanently add a ban rule?
On CentOS 7, the default firewall is "firewalld", and you can configure it with "firewall-cmd". You can use it to add temporary or permanent rules. You can read the man page of that to learn how to view, add, modify or delete rules.
Personally though, I find firewalld to be cumbersome, so I remove it completely, and installed instead "iptables-services".
yum erase firewalld yum install iptables-services
Then, after adding your iptables rule(s), run:
iptables-save > /etc/sysconfig/iptables ip6tables-save > /etc/sysconfig/ip6tables
They'll be applied at boot.
Regards, Anand
On Sun, Apr 19, 2020 at 9:45 AM Anand Buddhdev anandb@ripe.net wrote:
Personally though, I find firewalld to be cumbersome, so I remove it completely, and installed instead "iptables-services".
Ya, i agonized over accepting firewalld. I'm a smalltime manager who wears many hats and doesn't have alot of time to practice sysadmin skills. It took me about 5 years to get confident with iptables and go from fresh install to company firewall in one sitting. Now that I've adopted firewalld which has a wider variety of command/rule statements, I am constantly hitting "man firewall-cmd" and cannot competently recall iptables in any comprehensible way; it's like mixing Japanese and English whenever I try to communicate with a centos box firewall, heh.
--On Sunday, April 19, 2020 10:30 AM -0400 Jeffrey Walton noloader@gmail.com wrote:
Ugh, thanks. I did not realize the changes were only temporary.
What is the recommended way to permanently add a ban rule?
service iptables save
That runs the initscript that knows how to save the running firewall to /etc/sysconfig.
On Sun, Apr 19, 2020 at 8:58 AM Jeffrey Walton noloader@gmail.com wrote:
Hi Everyone,
We rent a CentOS 7 VM from GoDaddy. We received a warning about excessive cpu usage, and a threat to cancel our service. We tracked it down to Apache and someone hammering our web server.
The offending host is 59.64.129.175. To err on the side of caution we attempted to block the entire netblock. According to whois data, that's 59.64.128.0-59.64.159.255.
iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROPAfter reboot cpu usage is still high and access_log still shows useless requests from the host:
59.64.129.175 - - [19/Apr/2020:08:53:53 -0400] "GET /w/index.php?title=Special:WhatLinksHere&limit=50& printable=yes HTTP/1.1" 301 311I seem to be missing something. That's not surprising since I am not a server administrator.
How do I filter the unwanted traffic from the netblock?
Thanks Mike and Mark.
This is where I am at... I'm following https://www.howtogeek.com/177621/the-beginners-guide-to-iptables-the-linux-f... because GoDaddy has not published any documents on this (other then use cPanel, which I don't have access to).
The rule is persisted but it is being ignored.
# iptables -L | grep policy Chain INPUT (policy ACCEPT) Chain FORWARD (policy ACCEPT) Chain OUTPUT (policy ACCEPT)
# iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROP # /sbin/service iptables save iptables: Saving firewall rules to /etc/sysconfig/iptables: [OK]
<reboot, top still shows high usage, logs still show requests from offender>
# iptables -L Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED ACCEPT icmp -- anywhere anywhere ACCEPT all -- anywhere anywhere ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:ssh ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:http ACCEPT tcp -- anywhere anywhere state NEW tcp dpt:https REJECT all -- anywhere anywhere reject-with icmp-host-prohibited DROP tcp -- 59.64.128.0/19 anywhere
Chain FORWARD (policy ACCEPT) target prot opt source destination REJECT all -- anywhere anywhere reject-with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT) target prot opt source destination
We really need the server to honor this rule. How do we get CentOS to use this rule?
Jeff
Insert the rule early in the chain. To determine where, I use this command:
iptables -L INPUT -v -n --line-numbers
You should put the new rule before rule 1, I think, so it takes effect before even the ESTABLISHED rule from the connection tracker.
Use this:
iptables -I INPUT 1 -s 59.64.128.0/19 -p TCP -j DROP
If you think you'll build up a list of attackers, you can use an ipset, instead. I use firewalld for my own firewalls, which has integral support for saving and restoring ipsets. You can use a firewalld "direct" rule to insert an ipset-based ban before other rules in the INPUT chain.
Am 19.04.2020 um 14:58 schrieb Jeffrey Walton:
The offending host is 59.64.129.175. To err on the side of caution we attempted to block the entire netblock. According to whois data, that's 59.64.128.0-59.64.159.255.
iptables -A INPUT -s 59.64.128.0/19 -p TCP -j DROP
There was no comment so far that the order of the iptables rules matters. With your command you append to the existing rules. If would be without effect in case there is a rule in order before which permits the traffic you try to block.
After reboot cpu usage is still high and access_log still shows useless requests from the host:
59.64.129.175 - - [19/Apr/2020:08:53:53 -0400] "GET /w/index.php?title=Special:WhatLinksHere&limit=50& printable=yes HTTP/1.1" 301 311I seem to be missing something. That's not surprising since I am not a server administrator.
How do I filter the unwanted traffic from the netblock?
The iptables rules should be saved in /etc/sysconfig/iptables to be read in at boot time (or when the iptables services gets restarted).
Alexander
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Alexander Dalloz -
Anand Buddhdev -
Jeffrey Walton -
Kenneth Porter -
Mark (Netbook) -
Mike