Address list - capture connections to public IPs not alocated

Hi,

I am tiring to capture in an Address list the traffic to my IPs in a public class that are not allocated to any machine.
I have created the following firewall rule, but after running it for some time it ends with banning traffic even to legit sources like Yahoo, Google …etc.

add action=add-src-to-address-list address-list=drop_traffic chain=forward src-address=![public IP class] dst-address=[public IP class] dst-address-list=![UsedIPs]

Where [UsedIPs] is an address list containing all the public class IPs that are in use.

Thank you in advance