A firewall is an essential element for any PC. Thanks to it your ports are free of invaders and blockages, stopping external threats from accessing via the Internet.
If, at these levels, you still don`t have a firewall, a good option is this VisNetic Firewall. It is a firewall for both personal and LAN use, so that none of the PCs on that LAN will suffer unwanted access.
The restriction and protection options of VisNetic Firewall can be configured by the user.