Defines the set of Internet Control Message Protocol (ICMP) message types that Windows Firewall allows. Utilities can use ICMP messages to determine the status of other computers. For example Ping uses the echo request message. If you do not enable the “Allow inbound echo request” message type Windows Firewall blocks echo request messages sent by Ping running on other computers but it does not block outbound echo request messages sent by Ping running on this computer. If you enable this policy setting you must specify which ICMP message types Windows Firewall allows this computer to send or receive. If you disable this policy setting Windows Firewall blocks all the listed incoming and outgoing ICMP message types. As a result utilities that use the blocked ICMP messages will not be able to send those messages to or from this computer. If you enable this policy setting and allow certain message types then later disable this policy setting Windows Firewall deletes the list of message types that you had enabled. If you do not configure this policy setting Windows Firewall behaves as if you had disabled it. Note: If any policy setting opens TCP port 445 Windows Firewall allows inbound echo requests even if the “Windows Firewall: Allow ICMP exceptions” policy setting would block them. Policy settings that can open TCP port 445 include “Windows Firewall: Allow file and printer sharing exception” “Windows Firewall: Allow remote administration exception” and “Windows Firewall: Define inbound port exceptions. “Note: Other Windows Firewall policy settings affect only incoming messages but several of the options of the “Windows Firewall: Allow ICMP exceptions” policy setting affect outgoing communication.