Windows includes a two-way, stateful-inspection, packet-filtering firewall. Windows Firewall is enabled by default for all connections, and it begins protecting your computer at boot. The following actions take place by default:

• The firewall blocks all inbound traffic, with the exception of traffic sent in response to a request sent by your computer and unsolicited traffic that has been explicitly allowed by creating a rule.
• All outgoing traffic is allowed unless it matches a configured rule.