It depends on what you mean by secure: the wireless signal itself IS NOT encrypted - so the data flowing from your client and the access point is unencrypted. The link from the AP to the Internet IS secured by a firewall, that blocks all the unauthorised traffic. This means, that someone might listen to your traffic (unless you make a VPN connection), but he won't be able to SPAM out from our network or to execute any port scanning or other nasty activities.