There are a number of possible causes, and that is only one possibility. It is very easy to secure your network -- use WPA2 personal with AES encryption, a new passkey, and turn off WPS if that is an option in your router. Also best to change your default router user ID and password -- and write everything down since you will need it again.
You should also download and run the free and very good Glary Utilities from
HERE. It will clean up your registry, clear out malware, and clean out temp files and caches. I use it often on many machines and it works very well.