Troubleshooting

Shared Folders Are Visible to the Internet

When I use Explorer to view my computer across the Internet, I am prompted for a username and password, and/or shared folders are visible.

If you have this problem, Microsoft file sharing services are being exposed to the Internet. If you have a shared connection to the Internet, you need to enable Windows Firewall, or enable filtering on your Internet connection. At the very least you must block TCP/UDP ports 137 through 139 and 445. Don't leave this unfixed!

If you have several computers connected to a cable modem with just a hub, and no connection sharing router, you should read Chapter 19 for alternate ways to share your cable Internet connection.

Sensitive Web Pages or FTP Folders Are Visible to the Internet

When I access my Web site from the Internet using a Web browser or anonymous FTP, I can view folders that I thought were private and protected.

First, you must be sure that the shared folders are not on a FAT-formatted disk partition. FAT disks don't support user-level file protection. Share only folders from NTFS-formatted disks.

You must restrict access on the shared folders using NTFS permissions. View the folders in Windows Explorer on the computer running IIS. View the folders' Securities Properties tab. Be sure neither Everyone nor IUSR_XXXX (where XXXX is your computer name) is granted access. On these protected folders, grant Read and Write privileges only to authorized users. In the Internet Information Services management console, you can also disable Anonymous access on the Web site's security page.

Can't View Protected Web Pages

When I try to view protected Web pages or change to a protected directory in FTP, I can't view the pages or folders.

View the virtual folder's Properties page in the Internet Information Services management applet. On the Directory Security tab, click Edit under Anonymous Access and Authentication Control. Be sure that Digest Authentication and Integrated Windows Authentication are checked. If they were checked already, view the folder's Security settings in Windows Explorer as described in the previous troubleshooting tip. Make sure that the desired users or groups are granted appropriate NTFS access permissions on the folder and its files and subfolders.

Network Services Are Not Being Blocked

I can connect to my computer across the Internet with remote administration tools such as the Registry Editor, with SNMP viewers, or with other tools that use network services. How do I prevent this access?

Look up the protocol type (for example, UDP or TCP) and port numbers of the unblocked services, and configure filters in your router to block these services. Your ISP might be able to help you with this problem. You might have disabled Windows Firewall by mistake.

Windows Messenger Can't Send Files

When you attempt to send someone a file using Windows Messenger, they can't receive the file.

When you send someone a file, what actually happens is that the other person's copy of Windows Messenger contacts your computer to pick up the file. If Windows Firewall is blocking Windows Messenger data, the other person's copy of Messenger will not be able to retrieve the file. Check the Windows Firewall configuration dialog to ensure that Don't Allow Exceptions is not checked (at least temporarily), and that Windows Messenger appears in the Exceptions list and is checked.

Router Is Accessible via Telnet

I can connect to my Internet service router through Telnet across the Internet without providing a secret administrative password. How do I prevent this access?

Configure your router to require a sensible password for access. Choose a password with letters and numbers. Be sure you write it down, and also give it to the technical support department of your ISP. The ISP might even be able to help you change the password.