Home > Articles > Networking

Network Security and Virtual Private Network Technologies

Network security can be a headache, especially when VPN technology is added to the mix. This chapter from the CCSP Self-Study text will help prepare you to deal with the complex security issues presented by virtual vrivate networks.
This chapter is from the book

After completing this chapter, you will be able to perform the following tasks:

  • Understand network security

  • Understand VPN technologies

  • Use the Cisco Security Wheel

  • Understand the basics of the IPSec protocol framework

This opening chapter provides an overview of network security and looks at the Cisco Architecture for Voice, Video, and Integrated Data (AVVID) and the SAFE blueprint. It also covers the IP Security (IPSec) framework and identifies the main encryption and algorithm protocols. Then it looks at how IPSec works before finishing with the five steps of IPSec operation. These five steps are very important to remember and also are very useful for implementing and troubleshooting any IPSec-based virtual private network (VPN), whether firewall-, router-, or VPN Concentrator-based.

Network Security Overview

Network security is essential because the Internet is a network of interconnected networks without a boundary. Because of this fact, the organizational network becomes accessible from and vulnerable to any other computer in the world. As companies become Internet businesses, new threats arise because people no longer require physical access to a company's computer assets: They can access everything over the public network.

In a recent survey conducted by the Computer Security Institute (CSI, http://www.gocsi.com), 70 percent of the organizations polled stated that their network security defenses had been breached and that 60 percent of the incidents came from within the organizations themselves.

Network security faces four primary threats:

  • Unstructured threats

  • Structured threats

  • External threats

  • Internal threats

Unstructured Threats

Unstructured threats consist of mostly inexperienced individuals using easily available hacking tools from the Internet. Some of the people in this category are motivated by malicious intent, but most are motivated by the intellectual challenge and are commonly called script kiddies. They are not the most talented or experienced hackers, but they have the motivation, which is all that matters.

Structured Threats

Structured threats come from hackers who are more highly motivated and technically competent. They usually understand network system designs and vulnerabilities, and they can understand as well as create hacking scripts to penetrate those network systems.

External Threats

External threats are individuals or organizations working outside your company who do not have authorized access to your computer systems or network. They work their way into a network mainly from the Internet or dialup access servers.

Internal Threats

Internal threats occur when someone has authorized access to the network with either an account on a server or physical access to the wire. They are typically disgruntled former or current employees or contractors.

The three types of network attacks are

  • Reconnaissance attacks

  • Access attacks

  • Denial of service (DoS) attacks

Reconnaissance Attacks

Reconnaissance is the unauthorized discovery and mapping of systems, services, or vulnerabilities. It is also called information gathering. In most cases, it precedes an actual access or DoS attack. The malicious intruder typically ping-sweeps the target network first to determine what IP addresses are alive. After this is accomplished, the intruder determines what services or ports are active on the live IP addresses. From this information, the intruder queries the ports to determine the application type and version as well as the type and version of the operating system running on the target host.

Reconnaissance is somewhat analogous to a thief scoping out a neighborhood for vulnerable homes he can break into, such as an unoccupied residence, an easy-to-open door or window, and so on. In many cases, an intruder goes as far as "rattling the door handle"—not to go in immediately if it is open, but to discover vulnerable services he can exploit later when there is less likelihood that anyone is looking.

Access Attacks

Access is an all-encompassing term that refers to unauthorized data manipulation, system access, or privilege escalation. Unauthorized data retrieval is simply reading, writing, copying, or moving files that are not intended to be accessible to the intruder. Sometimes this is as easy as finding shared folders in Windows 9x or NT, or NFS exported directories in UNIX systems with read or read-write access to everyone. The intruder has no problem getting to the files. More often than not, the easily accessible information is highly confidential and completely unprotected from prying eyes, especially if the attacker is already an internal user.

System access is an intruder's ability to gain access to a machine that he is not allowed access to (such as when the intruder does not have an account or password). Entering or accessing systems that you don't have access to usually involves running a hack, script, or tool that exploits a known vulnerability of the system or application being attacked.

Another form of access attacks involves privilege escalation. This is done by legitimate users who have a lower level of access privileges or intruders who have gained lower-privileged access. The intent is to get information or execute procedures that are unauthorized at the user's current level of access. In many cases this involves gaining root access in a UNIX system to install a sniffer to record network traffic, such as usernames and passwords, that can be used to access another target.

In some cases, intruders only want to gain access, not steal information—especially when the motive is intellectual challenge, curiosity, or ignorance.

DoS Attacks

DoS is when an attacker disables or corrupts networks, systems, or services with the intent to deny the service to intended users. It usually involves either crashing the system or slowing it down to the point where it is unusable. But DoS can also be as simple as wiping out or corrupting information necessary for business. In most cases, performing the attack simply involves running a hack, script, or tool. The attacker does not need prior access to the target, because usually all that is required is a way to get to it. For these reasons and because of the great damaging potential, DoS attacks are the most feared—especially by e-commerce website operators.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020