Use Encryption on Your Wireless Network

Once you go wireless, you should encrypt the information you send over your wireless network, so that nearby attackers can’t eavesdrop on these communications. Encryption scrambles the information you send into a code so that it’s not accessible to others. Using encryption is the most effective way to secure your network from intruders.

Two main types of encryption are available for this purpose: Wi-Fi Protected Access (WPA) and Wired Equivalent Privacy (WEP). Your computer, router, and other equipment must use the same encryption. WPA2 is strongest; use it if you have a choice. It should protect you against most hackers. Some older routers use only WEP encryption, which likely won’t protect you from some common hacking programs. Consider buying a new router with WPA2 capability.

Wireless routers often come with the encryption feature turned off. You must turn it on. The directions that come with your router should explain how. If they don't, check the company’s website.

source: https://www.consumer.ftc.gov/articles/0013-securing-your-wireless-network