Day 5: Remote Access

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Remote Access Protocols and Services from an Information Security Perspective

If you have taken the Network+ exam or worked with any large-scale networking operation before, you probably have some degree of familiarity with remote access protocols. The Security+ exam covers these Remote Access services a great deal and it would be almost impossible to pass the exam without a firm understanding of the tested Remote Access services and protocols. Below are the ones that you absolutely need to know and understand to do well on the Security+ examination. But first, we must answer the question: What is a remote access service?

Well, what is it?

A remote access service is one that allows a remote host to login to a network securely. Remote access is typically used in VPN and dial-up networking applications but can be used in other settings. Simply put, remote access services provide what the name implies. They provide confidentiality between the user of the remote network and the network.

Now we will look at the Security+ tested remote access services.

PPP

Point-to-Point Protocol, or PPP, is the most commonly used remote access protocol in the world. It is typically used to connect dial-up Internet users to the Internet (it is employed over the telephone system). It works through the TCP/IP stack and operates at the Network layer of the OSI model. It can use authentication protocols such as MS-CHAP, CHAP, EAP, PAP, and many others. (Authentication protocols are covered elsewhere.) PPP operates on the Client/Server model, or in other words, a PPP client would dial up to a server for access to a remote network.

RADIUS

RADIUS (Remote Access Dial-In User Service) is another remote access protocol in which the gateway to the network (usually a router) defers user authentication to a central RADIUS server. One of the problems with RADIUS is that it transfers some information in clear or unencrypted text.

TACACS+

Mostly similar to RADIUS, TACACS+ is Cisco’s implementation of a remote access protocol and allows for Kerberos authentication with TACACS+ authorization. It is designed to be more secure, efficient, and uses TCP 49 rather than a UDP port (as RADIUS does).

SSH

SSH provides a secure shell (as an alternative to Telnet) to a remote host over TCP 22. Rather than using clear text, SSH provides strong encryption so that data is difficult to intercept and/or interpret. SSH however does not provide remote dial-in access to networking as the previous services do. You should associate SSH with Telnet in that SSH basically provides remote control of a PC or server.

Telnet

Telnet is a service, similar to SSH, that provides remote access to a host. The difference between Telnet and SSH is that Telnet does not provide any kind of encryption as information and communications are sent in clear text. Telnet operates at TCP 23.

Quick Review

1. An AOL user complains that he is having connection issues. He complains that after dialing into the network, he gets no response. Which of the following would be a likely source of problems? a. IP b. Telnet c. SSH d. PPP 2. Which of the following might be used so that a network admin would be able to securely connect to and correct a server issue from the comfort of his home? a. Telnet b. SSH c. TCP/IP d. PPP e. CHAP

Answers

1. The only service from the list that provides dial-in networking reliably is (D) PPP 2. SSH (unlike Telnet) can SECURELY connect to a remote host and obtain a secure shell. ([[Image:|user posted image]]

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