Wireless networking can be kind of scary from a security standpoint. It opens up whole new attack vectors that were not present with wired network infrastructures. That doesn’t mean you can’t do it securely, however, and I aim to give you some ideas that can help you in that regard.
Many of these tips are likely to be inapplicable to a lot of people. For instance, if you’re running a wireless network that has to allow connections from a changing lineup of computers so that the specific computers on the network will not be constant, the point about restricting access by MAC address is unlikely to do much good. As always, you must exercise some common sense when reading through a list of security tips like this. You have to determine what options apply to you, and whether the fact that your plans make a given suggestion unusable means your plans are wrong or the suggestion simply is not relevant in your case.
Use a strong password. As I pointed out in the article A little more about passwords, a sufficiently strong password (on a system with decent password protection) makes the likelihood of cracking the password through brute force attacks effectively impossible. Using a sufficiently weak password, on the other hand, almost guarantees that your system will be compromised at some point.
Don’t broadcast your SSID. Serious security crackers who know what they are doing will not be deterred by a hidden SSID — the “name” you give your wireless network. Configuring your wireless router so it doesn’t broadcast your SSID does not provide “real” security, but it does help play the “low hanging fruit” game pretty well. A lot of lower-tier security crackers and mobile malicious code like botnet worms will scan for easily discovered information about networks and computers, and attack those that have characteristics that make them appear easy to compromise. One of those is a broadcast SSID, and you can cut down on the amount of traffic your network gets from people trying to exploit vulnerabilities on random networks by hiding your SSID. Most commercial grade router/firewall devices provide a setting for this.
Use good wireless encryption. WEP is not exactly “good” encryption. With a freely available tool like aircrack, you can sniff wireless traffic protected by WEP and crack security on that network in a matter of minutes. WPA is the current, common encryption standard you should probably be using — though, of course, you should use something stronger as soon as it becomes available to you. Technology is advancing every day, on both sides of the encryption arms race, after all.
Use another layer of encryption when possible. Don’t just rely on wireless encryption to provide all your security on wireless networks. Other forms of encryption can improve the security of the systems on the network, even if someone happens to gain access to the network itself. For instance, OpenSSH is an excellent choice for providing secure communications between computers on the same network, as well as across the Internet. Using encryption to protect your wireless network does not protect any communications that leave the network, so encryption schemes like SSL for dealing with e-commerce Websites is still of critical importance. The fact you’re using one type of encryption in no way suggests you should not be using other types of encryption as well.
Restrict access by MAC address. Many will tell you that MAC address restriction doesn’t provide real protection but, like hiding your wireless network’s SSID, restricting the MAC addresses allowed to connect to the network helps ensure you are not one of the “low hanging fruits” that people prefer to attack. It is best to be effectively invulnerable to the expert security cracker, but there’s nothing wrong with being less palatable to the amateur as well.