This likely does not apply to most VSPs, but our clients are confined to about 10 IPs and our upstream provider has about 6. The only solution I found is to block everything but these. However, before that fix, I found that EVERY attempt to hack in was via IP Address. We use the multidomain setup, so no number@ipaddresss will ever work, they must be @<fqdn>. From: FreeSWITCH-users <freeswitch-users-bounces@lists.freeswitch.org> On Behalf Of Lloyd Aloysius Sent: Tuesday, September 24, 2019 8:27 AM To: FreeSWITCH Users Help <freeswitch-users@lists.freeswitch.org> Subject: [Freeswitch-users] Security - IPtables, Fail2Ban, Rate Limit .. Recently see lots of attacks. Try to protect the system. Currently using iptables and fail2ban. It is not enough. I see the following page explain rate limit. https://freeswitch.org/confluence/display/FREESWITCH/Security # Trixter's SIP rate limiter (This helps protect you from DoS attacks) iptables -A INPUT -p udp --dport 5060 -m limit --limit 5/s --limit-burst 5 -i eth0 -j REJECT iptables -A INPUT -p udp --dport 5080 -m limit --limit 5/s --limit-burst 5 -i eth0 -j REJECT What is the best limit for 500 phones. Is there any other best practice to protect the system for Dos attacks. Thanks Lloyd