Wireless security isn't perfect, however WPA2 security has been as good as it gets for most residential (and business) wireless access points. Mostly all modern WiFi networks use the WPA2 security model and recently, a serious WPA2 vulnerability has been discovered by Mathy Vanhoef of inec-DistriNet. Mathy has a fantastic write-up and demonstration of what he is calling "Key reinstallation attacks (KRACKs)" - or the 'KRACK Attack'.
Microsoft Security Essentials
It's very controversial that antivirus software is something that I DON'T use :). In most cases, the software is more harmful than having an actual virus. I enjoy discussing the issue but unfortunately out of scope for this post. If you must use antivirus software personally, use Microsoft's Security Essentials. It's free for home users and updates automatically via Microsoft Update. Security Essentials has recently been rated #1 by several major tech publications.