Windows 2000 IPSec

IPSec stands for Internet Protocol Security and it is used to encrypt TCP/IP data so the information cannot be captured and understood by outsiders. It is used both on internal networks and between two private networks over the internet to support virtual private networking (VPN). Terms:

• Transport mode - The data portions of the packet are encrypted.
• Tunnel mode - The data and address portions of the message are both encrypted and that packet is used in the data portion of a new packet of a new IP packet with a new address. It is used between two routers for VPN.

Security Methods

IPSec can use various security encryption algorithms and key lengths. These are the characteristics of IPSec connections (security methods):

• A specified encryption algorithm.
• A negotiated key length.
• A negotiated key lifetime.

Supported Authentication Methods

• A shared secret such as a key or phrase.
• Kerberos
• Certificates - The certificate can only be created using a private key and the certificate is verified using the public key. This way the certificate can be used for authentication.

Enabling

Enabling IPSec is enabled on individual computers by using the "Network and Dial-up Connections folder". The "Domain Security Policy" administrative tool is used to enable IPSec on all computers or domain controllers in a domain. "Active Directory Users and Computers" can be used to set up a group policy object which can enable IPSec on Windows 2000 computers in an organizational unit. IPSec can be managed by using the Microsoft Management Console (MMC) IP Cecurity Policy Snap-in.

When using group policy to set IPSec, the following options are available:

• Client (Respond Only) - Only Uses IPSec to respond to requests for use of IPSec but outgoing requests are done with normal communications.
• Server (Request Security) - Always uses IPSec for outgoing communications. Computers without IPSec enabled can still communicate with computers set in this mode.
• Secure Server (Require Security) - Uses IPSec for all communications. Computers without IPSec enabled can not communicate with computers set in this mode.

One IPSec policy may be set for one computer which includes one or more rules which are applied from the most restrictive to the least restrictive. IPSec Rules:

• IP Filter - Defines the type of traffic the rule applies to.
• IP Filter Action - Determines how the type of traffic is handled such as requiring encryption, requesting encryption for outgoing traffic, or allowing traffic that is not encrypted.
• Authentication Method - Three methods are Windows 2000 default, Keberos 5, or use an encryption key.
• Tunnel Setting - Determines whether IPSec will work in transport ("This rule does not specify a tunnel") or tunnel mode ("The tunnel endpoint is specified by this IP address").
• Connection Type - Determines if the rule applies to the local area network, all network connections or to remote access.

IPSec policy is set using "Active Directory Users and Computers".

The Security Monitor tool is used to monitor IPSec. Although it is a graphical tool, it is started from the command line by typing "Ipsecmon" followed by the name of the computer to be monitored.

IPSec Monitoring Tool

The IPSec monitoring tool can be used to provide a summary of the local computer IPSec connections. This tool can be started by clicking on "Start", "Run" and entering "ipsecmon.exe" and pressing the ENTER key.