I've setted some main ports - 20, 21, 22, 23, 53, 80, 443 for incoming and outgoing TCP connections.
If i want to connect from inside my server to another ftp server, it uses random UDP port in range 30000-60000. So i decided to make an iptables rule:
iptables -A INPUT -p udp -m multiport --dports 1:65535 -j ACCEPT
Generally, is it safe to leave this rule? Is there any type of attacks to UDP port? Thank you.