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Windows 2003-based computers support several methods of controlling inbound access. One ofthe most simple and most powerful methods of controlling inbound access is to use the TCP/IP

filtering feature. TCP/IP filtering is available on all Windows 2003-based computers.

TCP/IP filtering helps with security because it works in kernel mode. In contrast, other methods

of controlling inbound access to Windows 2003-based computers, such as by using the IPSecPolicy filter and the Routing and Remote Access server, depend on user-mode processes or theWorkstation and Server services.

You can layer your TCP/IP inbound access control scheme by using TCP/IP filtering with IPSec

filters and Routing and Remote Access packet filtering. This approach is especially useful if youwant to control both inbound and outbound TCP/IP access, because TCP/IP security alone

controls only inbound access.

Note TCP/IP filtering can filter only inbound traffic and cannot block ICMP messages,regardless of the settings that are configured in the Permit Only IP Protocols column or

whether you do not permit Internet Protocol 1. Use IPSec Policies or packet filtering if you needmore control over outbound access.

Note We recommend that you use the Configure E-mail and Internet Connection Wizard on SBS

2003-based computers with two network adaptors, and that you turn on the Firewall option andthen open the required ports on the external network adaptor. For more information about the

Configure E-mail and Internet Connection Wizard, click Start, and then click Help and Support.In the Search box, type Configure E-mail and Internet Connection Wizard, and then click Start

Searching. You can find information about the Configure E-mail and Internet ConnectionWizard in the Small Business Server Topics result set list.

Configuring TCP/IP security in Windows Server 2003

To configure TCP/IP security:

1. ClickStart, point to Control Panel, point to Network Connections, and then click thelocal area connection that you want to configure.

2. In the Connection Status dialog box, clickProperties.3. ClickInternet Protocol (TCP/IP), and then clickProperties.4. In the Internet Protocol (TCP/IP) Properties dialog box, clickAdvanced.5. ClickOptions.6. UnderOptional settings, clickTCP/IP filtering, and then clickProperties.7.

Click to select the

Enable TCP/IP Filtering (All adaptors) check box.

Note When you select this check box, you enable filtering for all adaptors, but youconfigure the filters individually for each adaptor. The same filters do not apply to alladaptors.

8. In the TCP/IP Filtering dialog box, there are three sections where you can configurefiltering for TCP ports, User Datagram Protocol (UDP) ports, and Internet protocols. For

each section, configure the security settings that are appropriate for your computer.

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Note When Permit All is activated, you permit all packets for TCP or UDP traffic.

Permit Only lets you to permit only selected TCP or UDP traffic by adding the allowedports. To specify the ports, you use the Add button. To block all UDP or TCP traffic,

clickPermit Only but do not add any port numbers in the UDP Ports column orTCP

Ports column. You cannot block UDP or TCP traffic by selecting Permit Only for IPProtocols and excluding IP protocols 6 and 17.

Configuring TCP/IP security in Windows Small Business Server 2003

To configure TCP/IP Filtering, follow these steps.

Note To perform this procedure, you must be a member of the Administrators group or theNetwork Configuration Operators group on the local computer.

1. ClickStart, point to Control Panel, right-clickNetwork Connections, and then clickOpen.

2. Right-click the network connection where you want to configure inbound access control,and then clickProperties.

3. UnderadaptorName Connection Properties on the General tab, clickInternetProtocol (TCP/IP), and then clickProperties.

4. In the Internet Protocol (TCP/IP) Properties dialog box, clickAdvanced.5. Click the Options tab.6. ClickTCP/IP Filtering, and then clickProperties.7. Click to select the Enable TCP/IP Filtering (All adaptors) check box.

Note When you select this check box, you enable filtering for all adaptors. However,

filter configuration must be completed on each adaptor. When TCP/IP Filtering isenabled, you can configure each adaptor by selecting the Permit All option, or you couldallow for only specific IP protocols, TCP ports, and UDP ports to accept inbound

connections. For example, if you enable TCP/IP Filtering and you configure the externalnetwork adaptor to permit only port 80, this lets the external network adaptor to accept

Web traffic only. If the internal network adaptor also has TCP/IP Filtering enabled but isconfigured with the Permit All option selected, this enables unrestricted communication

on the internal network adaptor.8. UnderTCP/IP Filtering, there are three columns with the following labels:

o TCP Portso UDP Portso

IP Protocols

In each column, you must select one of the following options:

o Permit All. Select this option if you want to permit all packets for TCP or UDPtraffic.

o Permit Only. Select this option if you want to permit only selected TCP or UDPtraffic, clickAdd, and then type the appropriate port or protocol number in the

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Add Filter dialog box. You cannot block UDP or TCP traffic by selecting PermitOnly in the IP Protocols column and by then adding IP protocols 6 and 17.

Note You cannot block ICMP messages, even if you select Permit Only in the IP

Protocols column and then you do not include IP protocol 1.

TCP/IP Filtering can filter only inbound traffic. This feature does not affect outbound traffic or

TCP response ports that are created to accept responses from outbound requests. Use IPSec

Policies or Routing and Remote Access packet filtering if you require more control over

outbound access.

Note If you select Permit Only in UDP Ports, TCP Ports, or the IP Protocols column and the

lists are left blank, the network adaptor will not be able to communicate with anything over a

network, either locally or to the Internet.