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Virtually all forms of Internet connections use some type of external modem, which acts as a bridge between the Internet and your PC or your local network. Many, if not most, of these modems are just modems, and they do not include other functionality such as a router or a switch. Some modems include a built-in router, and others include both a router and a switch. There is an important distinction between them, and you need to know the ramifications before you use them.
The most important thing you can do for security when using a broadband Internet connection is to ensure that you are connected though a router, which acts as a gateway with a hardware firewall between your local network and the Internet. A router includes a Dynamic Host Configuration Protocol (DHCP) server, which enables it to automatically assign private Internet Protocol (IP) addresses to systems on your network. Then, after the addresses are assigned, the router uses Network Address Translation (NAT) to translate packets moving between the private IP addresses on your network and the publicly visible IP address assigned to the router itself. Using NAT, only the router is publicly visible on the Internet; all the systems behind it are effectively hidden. This provides a hardware firewall to protect the PCs on your network.
If your modem includes multiple Ethernet ports for connecting PCs, most likely it has both a router and a switch built in. In that case, you can connect PCs to the modem/router, and the built-in router will protect your systems. If your modem has only a single port, that means it definitely doesn’t include a switch and might or might not include a router. If it does include a router, and you only want to connect a single PC, you can connect it directly to the Ethernet port. However, if it doesn’t include a router, you need to connect the Ethernet port on the modem to the WAN port on a router and then connect your PC or network to the router.
To determine whether your modem includes a router, consult the manufacturer documentation. If the modem includes a DHCP server and NAT functionality, it has a router. If not, it’s just a bare modem with no built-in router.
To secure your network, do the following:
- Change the default password for the router’s administrator.
- Change the default SSID for a wireless router—An unauthorized user can look up documentation for a router based on the default SSID and learn default passwords, IP addresses, and other information that can be used to hack your network.
- Use WPA2 encryption with a strong encryption key on your wireless router; all connections to the router must provide the same SSID, encryption type, and encryption key to make a connection.
- Configure wireless routers to accept only wired connections for management (viewing or changing settings).
- Log the MAC addresses of users who connect to the network and check periodically for unfamiliar devices; use the MAC address filter feature to block unauthorized network devices.
- Limit the number of IP addresses to those you actually need for your client PCs and devices. If your router is configured to supply more IP addresses than devices, unauthorized users can use them.
- Use anti-malware software, including a software firewall and anti-virus, on all computers and devices connected to your home network. Note that Android and iOS devices as well as PCs can be targeted, and some malware attacks mobile devices as a way to reach their ultimate target, your PCs.
- Use the Public or block all incoming traffic firewall option for Internet connections made in public places to block all unsolicited incoming traffic.
- With Windows 7 and newer, use the Home firewall option for a home network (especially if you are going to set up a homegroup).
- With Windows Vista or newer, use the Work or Office firewall options for other types of workgroup networks.
- If only Windows 7 or newer users and supported devices are on a home network, set up a homegroup, which is a secure network.
To learn more about TCP/IP, the network protocol used for Internet access, see the section “IP and TCP/IP,” in Chapter 16, “Local Area Networking.”