Windows 7 / Networking

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Packet Filters

Packet filtering enables an administrator to specify the type of inbound and outbound traffic that is allowed to pass through a Windows Server 2008 router. When configuring packet filters, you can allow all traffic except traffic prohibited by filters. Or you can deny all traffic except traffic that is allowed by filters.

To add a packet filter, follow these steps:

1. Open Routing and Remote Access.
2. In the console tree, click General under Routing and Remote Access/Server Name/[IPv4 or IPv6].
3. In the details pane, right-click the interface on which you want to add a filter, and then click Properties.
4. On the General tab, click either Inbound Filters or Outbound Filters.
5. In the Inbound Filters or Outbound Filters dialog box, click New.
6. In the Add IP Filter dialog box, type the settings for the filter, and then click OK.
7. In Filter action, select the appropriate filter action, and then click OK.

After a packet filter is created, you can edit it at any time by selecting the filter from the list and clicking Edit.

Windows Firewall

Windows Firewall is a packet filter and stateful host-based firewall that allows or blocks network traffic according to the configuration. A packet filter protects the computer by using an access control list (ACL), which specifies which packets are allowed through the firewall based on IP address and protocol (specifically the port number). A stateful firewall monitors the state of active connections and uses the information gained to determine which network packets are allowed through the firewall. Typically, if the user starts communicating with an outside computer, it remembers the conversation and allows the appropriate packets back in. If an outside computer tries to start communicating with a computer protected by a stateful firewall, those packets are dropped automatically unless access was granted by the ACL.

Windows Firewall is on by default. Any program or service that needs to communicate on a network must be opened in a firewall, including sharing files, pinging the server, or providing basic services, such as DNS and DHCP.

Compared to Windows Firewall introduced with Windows XP SP2, the Windows Firewall used with Windows Server 2008 has some major improvements, including the following:

• Windows Firewall supports IPv6 connection filtering.
• By using outbound packet filtering, you can help protect the computer againt spyware and viruses that attempt to contact outside computers.
• With the advanced packet filter, rules can also be specified for source and destination IP addresses and port ranges.
• Rules can be configured for services by the service name chosen from a list, without needing to specify the full path filename.
• IPSec is fully integrated with Windows Firewall, allowing connections to be allowed or denied based on security certificates, Kerberos authentication, and so on. Encryption can also be required for any kind of connection.
• A new management console snap-in named Windows Firewall with Advanced Security provides access to many advanced options and enables remote administration.
• You can use separate firewall profiles for when computers are domainjoined or connected to a private or public network.

Basic Configuration

Windows Firewall is on by default. When Windows Firewall is on, most programs are blocked from communicating through the firewall. If you want to unblock a program, you can add it to the Exceptions list (on the Exceptions tab). For example, you might not be able to send photos in an instant message until you add the instant messaging program to the Exceptions list. To add a program to the Exceptions list, click the Add program button and select it from the available list or browse for it by clicking the Browse button.

To turn on or off Windows Firewall, follow these steps:

1. Open Windows Firewall by clicking the Start button, clicking Control Panel, clicking Security, and then clicking Windows Firewall.
2. Click Turn Windows Firewall On or Off. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
3. Click On (recommended) or Off (not recommended) and then click OK.

If you want the firewall to block everything, including the programs selected on the Exceptions tab, select the Block All Incoming Connections check box. Block All Incoming Connections blocks all unsolicited attempts to connect to your computer. Use this setting when you need maximum protection for your computer, such as when you connect to a public network in a hotel or airport, or when a computer worm is spreading over the Internet. With this setting, you are not notified when Windows Firewall blocks programs, and programs on the Exceptions list are ignored.

The Windows Firewall Settings interface has three tabs:

• General: Enables you to turn Windows Firewall on and off, as well as to block all incoming connections, no matter how you have configured the exceptions.
• Exceptions: Enables you to configure programs and ports for which you want to allow communication into and out from your Windows Vista computer. Only create an exception that is specifically required, and remove exceptions that you no longer need. Never create an exception for a program when you are unsure of the functionality of that program.
• Advanced: Enables you to select the network interfaces that you want Windows Firewall to protect.

To configure programs as exceptions,

1. Open Windows Firewall by clicking Start → Control Panel → Security → Windows Firewall.
2. Click Allow a program through Windows Firewall. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
3. In the Windows Firewall dialog box, select the Exceptions tab and then click Add Program.
4. In the Add A Program dialog box, select the program in the Programs list or click Browse to use the Browse dialog box to find the program.
5. By default, any computer, including those on the Internet, can access this program remotely. To restrict access further, click Change Scope.
6. Click OK three times to close all open dialog boxes.

To open a port in Windows Firewall,

1. Open Windows Firewall by clicking the Start button, clicking Control Panel, clicking Security, and then clicking Windows Firewall.
2. Click Allow a program through Windows Firewall. If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
3. Click Add port.
4. In the Name box, type a name that will help you remember what the port is used for.
5. In the Port number box, type the port number.
6. Click TCP or UDP, depending on the protocol.
7. By default, any computer, including those on the Internet, can access this program remotely. To change scope for the port, click Change scope, and then click the option that you want to use. ("Scope" refers to the set of computers that can use this port opening.)
8. Click OK two times to close all open dialog boxes.