iptables
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iptables [2010/02/04 22:02] k2patel |
iptables [2020/08/10 02:35] |
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| - | ====== IPTABLES ====== | ||
| - | |||
| - | Statefull and Powerfull Firewall.\\ | ||
| - | |||
| - | ==== Enable for SSH Bruteforce Prevention ==== | ||
| - | This is not a 100% proof setup as it does not block based on the result of authentication.\\ | ||
| - | It just work based on connection.\\ | ||
| - | |||
| - | === Simple Rules === | ||
| - | <code bash> | ||
| - | iptables -N BRTBLK | ||
| - | iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j BRTBLK | ||
| - | iptables -A BRTBLK -m recent --set --name SSH | ||
| - | iptables -A BRTBLK -m recent --update --seconds 45 --hitcount 5 --name SSH -j DROP | ||
| - | </code> | ||
| - | |||
| - | === Rules With Exceptions === | ||
| - | Replace <Exception> with your IP.\\ | ||
| - | You can use multiple rules with diff. IP to allow exceptions. | ||
| - | |||
| - | <code bash> | ||
| - | iptables -N BRTBLK | ||
| - | iptables -A INPUT -p tcp --dport 22 -s <Exception> -j ACCEPT | ||
| - | iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j BRTBLK | ||
| - | iptables -A BRTBLK -m recent --set --name SSH | ||
| - | iptables -A BRTBLK -m recent --update --seconds 45 --hitcount 5 --name SSH -j DROP | ||
| - | </code> | ||
| - | |||
| - | === Rules to Log Bloked IP === | ||
| - | |||
| - | <code bash> | ||
| - | iptables -N BRTBLK | ||
| - | iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j BRTBLK | ||
| - | iptables -A BRTBLK -m recent --set --name SSH | ||
| - | iptables -A BRTBLK -m recent --update --seconds 45 --hitcount 5 --name SSH -j LOG --log-level info --log-prefix "Bad IP : " | ||
| - | iptables -A BRTBLK -m recent --update --seconds 45 --hitcount 5 --name SSH -j DROP | ||
| - | </code> | ||
| - | |||
| - | ==== Force SYN packets check ==== | ||
| - | Make sure NEW incoming tcp connections are SYN packets; otherwise we need to drop them: | ||
| - | |||
| - | <code bash> | ||
| - | iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP | ||
| - | </code> | ||
| - | |||
| - | ==== Force Fragments packets check ==== | ||
| - | Packets with incoming fragments drop them. This attack result into Linux server panic such data loss. | ||
| - | |||
| - | <code bash> | ||
| - | iptables -A INPUT -f -j DROP | ||
| - | </code> | ||
| - | |||
| - | ==== XMAS packets ==== | ||
| - | Incoming malformed XMAS packets drop them: | ||
| - | |||
| - | <code bash> | ||
| - | iptables -A INPUT -p tcp --tcp-flags ALL ALL -j DROP | ||
| - | </code> | ||
| - | |||
| - | ==== Drop all NULL packets ==== | ||
| - | Incoming malformed NULL packets: | ||
| - | |||
| - | <code bash> | ||
| - | iptables -A INPUT -p tcp --tcp-flags ALL NONE -j DROP | ||
| - | </code> | ||
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iptables.txt ยท Last modified: 2020/08/10 02:35 (external edit)
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