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Chapter 7

Network Security. Chapter 7. Overview. Threats to Network Security Implementing Security Measures Applying Patches and Upgrades Firewalls . Threats to Network Security. Overview: Internal/External Security. The Internet essentially works by following rules that are open to the public.

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Chapter 7

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  1. Network Security Chapter 7

  2. Overview • Threats to Network Security • Implementing Security Measures • Applying Patches and Upgrades • Firewalls

  3. Threats to Network Security

  4. Overview: Internal/External Security • The Internet essentially works by following rules that are open to the public. • If one studies the rules enough, one is bound to find loopholes and weaknesses that can be exploited. • The number of individuals, organizations, and institutions connected to the Internet are growing. • Connecting to the Internet opens the door to network intruders.

  5. Security vulnerabilities within Linux services • BIND Domain Name System • Remote Procedure Calls (RPC) • Apache Web Server • General UNIX Authentication Accounts with No Passwords or Weak Passwords • Clear Text Services • Sendmail • Simple Network Management Protocol (SNMP) • Secure Shell (SSH) • Misconfiguration of Enterprise Services NIS/NFS • Open Secure Sockets Layer (SSL)

  6. Well Known Exploits • Each combination of NOS and application software contains it’s own unique set of vulnerabilities and weaknesses. • Threats to network security comes from individuals with sophisticated tools. • Some of these individuals are often called "script kiddies". • Script kiddy is a negative term used to describe immature individuals that use scripts, software programs, or techniques created by other, more skilled crackers.

  7. Implementing Security Measures

  8. Secure Sockets Layer (SSL) • SSL was developed by Netscape to provide security for its web browser. • It uses public and private key encryption.

  9. Applying Patches and Upgrades

  10. Finding Patches and Upgrades • Patches are fixes to existing software code. • A NOS manufacturer typically provides security patches. • Microsoft now includes the option to use software called Windows Update with its operating systems.

  11. Selecting Patches and Upgrades • Software makers recommend installing software security patches immediately. • This is done to reduce exposure to known vulnerabilities. • Software venders release security updates as soon as they are available. • Understanding the effect on the system will help determine if an update, fix, or patch is necessary.

  12. Applying Patches and Upgrades • Periodically, NOS vendors issue updates to their network operating systems. These updates have various names: • Microsoft Service Packs • IBM Fixpacs • Novell Patches • These updates usually fix bugs or close security holes that have been found in the released version of the OS. • Download the updates from the network operating system vendor’s website.

  13. Firewalls

  14. Introduction to Firewalls and Proxies • A proxy is software that interacts with outside networks on behalf of a client host. • Typically, client hosts on a secure LAN request a web page from a server running proxy services. • The proxy server then goes out on the Internet to retrieve the web page. • The web page is then copied to the proxy server, this is referred to as caching.

  15. Introduction to Firewalls and Proxies • Administrators use NetworkAddress Translation (NAT) to alter the source address of packets originating from a secure LAN. • This allows secure LANs to be addressed using private IP addresses. • Private IP addresses are not routed on the Internet. • An outside hacker cannot directly reach a computer with a private address. • Some experts make a distinction between NAT and a firewall. Others look at NAT as part of a comprehensive firewall solution.

  16. Firewall Placement • A boundary router connects the enterprise LAN to its ISP or the Internet. • The boundary router should only allow HTTP, FTP, mail, and DNS related traffic to the DMZ. • The DMZ is designed to keep the inside network clean. • The NOS servers in the DMZ should be tightly configured.

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