While talking about computer security, we should also mention in a few words about network security. Currently, probably 90% of users use Wi-Fi - so it's worth to remind that you shlould never to leave your network unsecured!!!
While setting the WIFI password, try to make it extremely strong - in the case of a network access, using a difficult and long password is not a problem at all because you enter it only once (in one device) not every time you log in - so it's worth taking care of security.
You should also change the router administrator password, because the pair "admin" "admin" (or "admin" "12345") probably appears in 90% of routers.

Remember that if someone breaks into our network, he can also hack into our computers, files, spread virus, monitor traffic in our network, sniff our logins and passwords to websites and send spam or even use our network (IP address) for other illegal activities (like for example sharing/sending child pornography etc.)