Is there a way to prevent ad-hoc connections to a wifi portal?

Ad-hoc connections are computer to computer. You can't establish an ad-hoc connection to an access point or wi-fi portal. If you browse the available wireless connections and see an ad-hoc network, it's someone else's computer, not a connection to your wi-fi portal. In your wireless settings you can limit connections to infrastructure only. That will prevent incoming ad-hoc connections to your machine and prevent you from connecting to other ad-hoc networks inadvertantly.

This is a Tip of the Day by Kim Komando for setting up and protecting your Wi-Fi. This was in an email I get, so I'm copying it for you. I'm sure you can locate it at her site if you desire: www.kimkomando.com Most wireless routers are configured through your Internet browser. So you must connect your wireless router to a computer. Type your router's IP address into your browser's address bar. You can find the IP address in your router's manual. You'll be prompted for a user name and password. These will also be listed in your manual. You want to use WPA2 (Wi-Fi Protected Access) encryption to protect your network. You'll typically see this setting as WPA-PSK (pre-shared key). You'll be prompted to enter a password of eight to 63 characters--letters, numbers and symbols. The router will use the password to build an encryption key. WPA2 is the latest and safest version of WPA. The only weak point of WPA2 is your password. So make it as strong as possible. Here is a tip that will help. http://komando.com/tips/index.aspx?id=1503 Your router may use WPA, the forerunner to WPA2. If so, be sure your password has at least 21 characters. The earliest security standard is WEP (Wired Equivalent Privacy). Don't use that; it is easily broken. Check the router manufacturer's site for updates. If there aren't any, don't use the router to go online. Now you must update your computers. Click Start>>Control Panel. Double-click Network Connections. Right-click Wireless Network Connection. Select Properties from the pop-up menu and select the Wireless Networks tab. You should see your network listed under "Preferred networks." Select it and click Properties. If it's not listed, click the Add button. In the box labeled "Network name (SSID)," enter your network's name. Under Network Authentication, select WPA-PSK. Select AES under "Data encryption." Under "Network key," enter the same password you used for your router. You must enter it twice to confirm it. Make sure "The key is provided for me automatically" is not checked. Click OK>>OK.