MCP 70-299 : Module 12 Securing Remote Access

Lesson 3: Configuring Remote Access Clients

You can configure clients to connect to a remote access server in one of two ways: by using the network connection properties or by using the Connection Manager Administration Kit (CMAK). Manually configuring a connection by using network connection properties is convenient when you are using the default security settings or when you need to configure fewer than ten clients. However, it would not be possible to configure and maintain VPN or dial-up network connection configurations on hundreds or thousands of client computers.

The CMAK allows you to easily configure large numbers of clients by creating an executable file that you can distribute to your users. When your users run the file, it creates a dial-up or VPN connection with your customized security settings. If you later change authentication or encryption methods, you can re-run the CMAK and distribute a new executable file to overwrite the previous configuration. You can even automate the distribution of the CMAK executable file by distributing it with a Group Policy object.

Configuring Client-Side Authentication Protocols :

You create a remote access connection by using the New Connection Wizard, as described in Lesson 2, Exercise 2. However, the New Connection Wizard does not allow you to configure the acceptable authentication or encryption settings for the connection. To view or modify the authentication protocols enabled for a remote access connection on the client, open the properties dialog box of the dial-up or VPN connection on the client, and then click the Security tab.

The Typical option is selected, and a secured password and data encryption are required. Automatically Use My Windows Logon Name And Password is not selected. This default setting is the
more secure choice. If you choose to automatically use the current credentials, an intruder who takes over the active desktop of the client can successfully authenticate and connect to your internal network, potentially compromising far more than a single computer. When the option is cleared, the user must provide credentials each time a connection is made.

CMAK Wizard :

Manually configuring remote access connections on clients is straightforward, but configuring
hundreds or thousands of clients would be impossible. Unfortunately, you cannot use Group Policy objects to directly control a user’s available network connections. However, you can use the CMAK to create an executable file that you can deploy to users. When users run this file, the CMAK adds a connection by using the settings you specified with the CMAK wizard.

Though most of the pages of the wizard do not involve security settings, there are several important pages that you can use to control the security settings on the resulting network connection. Specifically, the VPN Entries and Dial-Up Networking Entries pages allow you to restrict authentication and encryption on the client. The VPN Entries and Dial-Up Networking Entries pages are identical, except that the VPN settings allow you to choose between PPTP and L2TP.

MCP 70-299 : 8 - Planning and Configuring IPSec

Lesson 1: IPSec Fundamentals

IPSec in the Windows Server 2003 operating system protects networks from active and passive attacks by securing IP packets through the use of packet filtering, cryptography, and the enforcement of trusted communication. IPSec is useful for improving the privacy and integrity of host-to-host, host-to-network, and network-to-network communications. IPSec can also be used as a host-based firewall to harden clients and servers by using packet filtering.

IPSec Overview :

IPSec is a framework of open standards for helping to ensure private, secure communications over Internet Protocol (IP) networks through the use of cryptographic security services. IPSec supports network-level data integrity, data confidentiality, data origin authentication, and replay protection. Because IPSec is integrated at the Internet layer (layer 3), it provides security for almost all protocols in the TCP/IP suite, and because IPSec is applied transparently to applications, there is no need to configure separate security for each application that uses TCP/IP.
IPSec can be used to provide packet filtering, to encrypt and authenticate traffic between two hosts, and to create a virtual private network (VPN). Using these capabilities of IPSec helps to provide protection against:
■ Network-based denial-of-service attacks from untrusted computers.
■ Data corruption.
■ Data theft.
■ User-credential theft.
■ Administrative control of servers, other computers, and the network.

Besides simply improving security, IPSec can be used to save money by enabling communications
between remote offices and remote access clients across the public Internet, rather than more costly dedicated circuits that offer privacy at the physical level.

Securing Host-to-Host Communications :

You can use IPSec to encrypt and validate the integrity of communications between two computers. For example, IPSec can protect traffic between domain controllers in different sites, between Web servers and database servers, or between Web clients and Web servers. When an IPSec client attempts to initiate a connection to an IPSec server, the client and server negotiate IPSec integrity and encryption protocols. After the IPSec connection is established, the application’s data is transported within the IPSec connection.
For example, consider the common scenario of a user downloading e-mail from a server using Post Office Protocol version 3 (POP3). If IPSec is not enabled, the e-mail client software initiates a connection directly to the e-mail server software. The user name and password will be transmitted in clear text, so that anyone with a protocol analyzer such as Network Monitor can intercept the user’s credentials. An attacker who has control of a router can modify the contents of the user’s e-mail messages as they are downloaded without being detected.

Securing Host-to-Network Communications :

IPSec is often used to authenticate and encrypt traffic sent directly between two hosts. However, IPSec can also protect traffic traveling from a single host to an entire network, as illustrated in Figure 8.2. This is most commonly used in remote access scenarios. In the past, many organizations required users to dial in to remote access servers connected to the organization’s private network. Today, organizations can eliminate the cost of maintaining dial-in servers by using IPSec to allow remote users to connect to an organization’s private network across the Internet. Most security experts agree that IPSec provides a level of security similar to that of dial-up remote access.

Securing Network-to-Network Communications :

IPSec can also be used to connect two remote networks. Before Internet connectivity was common, remote offices were connected with private links provided by communications companies. These links would typically consist of a circuit (such as a T1 in the United States or an E1 in Europe) from each of the remote offices that connected to a switched frame relay network that would carry the traffic over long distances.
Today, many organizations still use private links to connect offices. Private links offer some distinct advantages, most notably predictability and stability. Although the Internet continues to become more reliable, performance factors such as usable bandwidth, latency, and jitter fluctuate unpredictably. Private links dedicate bandwidth to a communication link and always follow the same path—guaranteeing that performance will always stay the same.