I am using a rather restrictive firewall on my machine, mostly to block potential port scanning. If any IP address sends me a unsolicited packet (packet that is not a response to my query) the IP address gets blocked for X minutes.
-A INPUT -i wlan0 -m recent --name PORTSCAN --update --seconds 300 -j DROP -A INPUT -i wlan0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A INPUT -i wlan0 -m recent --name PORTSCAN --set -j DROP
This rule never blocks legitimate websites. The only "legitimate" website that gets blocked are the stackexchange websites.
This happens constantly. I did not have time to investigate further, but the problem must be on your side, because I don't get these problems anywhere else.
Is your website scanning peoples machines ?