Thursday, July 23, 2009

Basic iptables rules


# If you use the kernel modules, make sure they are loaded
modprobe ip_tables
modprobe iptable_filter
modprobe iptable_mangle
modprobe iptable_nat
modprobe ipt_state
modprobe ipt_REJECT
modprobe ipt_LOG

# added in case you are reloading
iptables --flush

# drop all inbound by default
iptables -P INPUT DROP

# always allow loopback
iptables -A INPUT -i lo -j ACCEPT

# Allow return traffic
iptables -A INPUT -m state --state ESTABLISHED -j ACCEPT
iptables -A INPUT -m state --state RELATED -j ACCEPT

# Allow ICMP
iptables -A INPUT -p icmp -m icmp -j ACCEPT

## SSH (Limit connection attempts)
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --set
iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 60 --hitcount 4 -j DROP
iptables -A INPUT -p tcp -m tcp --source --dport 22 -j ACCEPT

# Log and Block
iptables -A INPUT -j LOG --log-prefix IN-FILTERBLOCK
iptables -A INPUT -j REJECT

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