*filter

# Set up logging for dropped packets
-N LOGDROP
-A LOGDROP -m limit --limit 15/min -j LOG --log-prefix "iptables dropped: " --log-level 7
-A LOGDROP -j DROP

# Allow all outbound traffic
-A OUTPUT -j ACCEPT

# Accept all loopback traffic
-A INPUT -i lo -j ACCEPT

# Drop all traffic to loopback IPs on other interfaces
-A INPUT ! -i lo -d 127.0.0.0/8 -j LOGDROP

# Accept incoming traffic related to established connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# Accept incoming traffic on TCP ports 22 (SSH), 80 (HTTP), 443 (HTTPS), and 5432 (Postgres)
-A INPUT -p tcp --dport   22 -j ACCEPT
-A INPUT -p tcp --dport   80 -j ACCEPT
-A INPUT -p tcp --dport  443 -j ACCEPT
-A INPUT -p tcp --dport 5432 -j ACCEPT

# Drop everything else
-A INPUT   -j LOGDROP
-A FORWARD -j LOGDROP

COMMIT