| 1.1 |  | Overview of Network Security |
| 1.1.1 |  | The need for network security |

| Security has one purpose, to protect assets. For most of history, this meant building strong walls to stop the bad guys, and establishing small, well-guarded doors to provide secure access for the good guys. This strategy worked well for the centralized, fortress-like world of mainframe computers and closed networks. The closed network typically consists of a network designed and implemented in a corporate environment, and provides connectivity only to known parties and sites without connecting to public networks. Networks were designed this way in the past and thought to be reasonably secure because of no outside connectivity.

With the advent of personal computers, LANs, and the wide-open world of the Internet, the networks of today are more open. As e-business and Internet applications continue to grow, finding the balance between being isolated and being open will be critical, along with the ability to distinguish the good guys from the bad guys. Furthermore, the rise of mobile commerce and wireless networks will be as the cannon was to the castle walls, exploding the old model and demanding that security solutions become seamlessly integrated, more transparent, and more flexible.

With the increased number of LANs and personal computers, the Internet began to create untold numbers of security risks. Firewall devices, which are software or hardware that enforce an access control policy between two or more networks, were introduced. This technology gave businesses a balance between security and simple outbound access to the Internet which was mostly used for e-mail and Web surfing.

This balance was short lived however as the use of extranets began to grow, which connected internal and external business processes. Businesses were soon realizing tremendous cost savings by connecting supply-chain management and enterprise resource planning systems to their business partners, and by connecting sales-force automation systems to mobile employees, and by providing electronic commerce connections to business customers and consumers. The firewall began to include intrusion detection, authentication, authorization, and vulnerability assessment systems. Today, successful companies have once again struck a balance by keeping the bad guys out with increasingly complex ways of letting the good guys in.

Most people expect security measures to ensure the following:

- Users can perform only authorized tasks.
- Users can obtain only authorized information.
- Users cannot cause damage to the data, applications, or operating environment of a system.

The word security means protection against malicious attack by outsiders, and involves controlling the effects of errors and equipment failures. Anything that can protect against an attack will probably prevent random misfortune as well.

Throughout this course many definitions, acronyms and logical device symbols dealing with security will be introduced . Refer to the glossary for further explanation when encountering unknown terms and acronyms.

| Resources FNS Graphic Icons

| Web Links National Institute of Standards and Technology Security Division (NIST) http://csrc.nist.gov/ Security Focus http://www.securityfocus.com/

Computer Security Institute
http://www.gocsi.com/

System Administration, Networking, and Security Institute or SANS
http://www.sans.org/newlook/home.htm

Carnegie Mellon Software Engineering Institute or CERT
http://www.cert.org

Cisco Security and VPN
http://www.cisco.com/en/US/netsol/
ns110/ns170/net_solution_home.html