Secure. Just make sure inbound netbios and other incoming ports and are blocked in firewall and/or block all local servers.
Wise incoming ports to block = 135, 137-179, 445, 515, 593, 1433, 1434
Use AES encryption for wireless (WPA2) with a long random password.
If you run a server, your security is only as good as the serving app you're using.