Personal Firewalls and Security Levels

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In the last posting I talked about selecting private (home network) or public (like a public hotspot). When protected behind a home router, telling the firewall to treat the network as a private network generally uses a less strict security policy that is appropriate when the other computers and devices on the local network can be trusted. Using a less strict security policy means less interference and fewer problems.

Problems can still happen, even when treating the network as a private network, so more firewall setting adjustments may be needed. Another broad setting most firewalls offer is some type of security level. Common names for security levels include high, medium, low, trusted, restricted, block-all, allow-all, and internet.

In some firewalls, a security level can be selected separately from the selection of private or public network, meaning that after setting the type of network, the security level can also be set. However, in some firewalls selecting the type of network is basically the same thing as selecting a security level. That is, instead of having both a network type and a security setting, there is only one setting that has choices like trusted (meaning private) and restricted (meaning public hotspot).

So what do different security levels mean? Regardless of the security level names, there is always an order of them from low to high. This ordering will be clear from the firewall user interface, such as listing them from top to bottom, with the lowest security level on the bottom. Each higher security level will block increasingly more things. Exactly what is blocked or allowed at each level is up to the firewall maker, but the things blocked or allowed are well-known services. These well-known services are often things that are built into the operating system. A good example of a well-known service is printer and file sharing. This service is commonly used on local networks. In fact, it is one of the most commonly used services on home networks, but it is not without some security risk so if it is not needed then it would be somewhat safer to turn it off.

How do you know what services you might need, and therefore what ones should be enabled and others blocked? Most people don't know, but the basic idea behind security levels is that instead of having to figure out exactly what services are needed, just pick a lower security level if you are having problems at the current level. By using this approach, you are essentially relying on the firewall maker, and the definition of their security levels, to block increasing more common and less risky services as one selects higher and higher security levels. So if the commonly used service you need isn't allowed at the current security level, there is a good chance that lowering one security level will unblock it. The firewall user interface or help information may provide at least a high-level description of what each security level allows or blocks.

One last thing to remember about changing the security level is that you may need to change it back again if you move your laptop to a public hotspot. Luckily many firewalls remember the security selection for each network type. So if you have high security selected for public networks (i.e., a hotspot) and low security selected for private networks (i.e., your home network), then switching from the private network setting to the public network setting will also cause the security level to be switched from low to high. Not all firewalls work this way, so be sure to check your firewall settings before joining a public hotspot.

So there you have the second easiest way to fix network problems caused by personal firewalls on a private home network – try a lower security level. This only works for common services. If you are having a problem with a custom service, or a less commonly used service, changing the security level probably won't help. I'll talk about how to deal with these problems in the next posting.

[#2]

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