And finally, if someone reaches 3 packets per minute, it is not only blocked, but send to TARPIT… Basically, this target never answer to the connecion packet, no reject, no accept, it simply forget the connection status to avoid filling the internal connection table and leave the connection half open, consuming entries in the outgoing connection table of the attacker, this will fill his table and potentially freeze his computer. I also log the blocked connection attempts, with another limiter to avoid filling the log file, no more than 10 messages are logged per minute. Given that related and established connection packet will be allowed by another rule, this one is only for incoming connections. No more than 3 packets are allowed in a 60 seconds window. SSH authentication rejects password authentication, but I will use the limit module to implement a rate limiter. I need to connect to this server, using SSH. A DNS -p tcp -tcp-flags FIN,SYN,RST,ACK SYN -dport 53 -j ACCEPT Reload the variablesĮnsure that the variables are available, by loading the configuration script : We need the WAN_* and LAN_* variable which is already defined in the configuration file, in 010 - Configuration variables. Masquerade (SNAT) non routable IPs forwarded to WAN.I use CHAOS and TARPIT rules against obvious attacker and ratelimiting rules, as passive replies to attacks. ![]() ![]() If someone gain access to my server an can execute a script, the script will probably be blocked to send the feedbacks to the attacker. I also prepare a default evolutive ruleset with one specificity : it forbids also OUTPUT connections by default. I will install a wrapper to persist the firewall rules on the disk and to automatically reload them at reboot. The Linux iptables firewall feature is already included in the kernel and the client application is already installed.
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