Home > Articles > Cisco Network Technology > General Networking > Network Security First-Step: Firewalls

Network Security First-Step: Firewalls

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Feb 8, 2012.

Chapter Description

This chapter dissects a firewall’s duties to understand what makes a firewall operate and how it does its job.

From the Book

Network Security First-Step

Network Security First-Step, 2nd Edition

$29.59 (Save 20%)

Firewalls Are “The Security Policy”

What kind of traffic is allowed into or out of your network? How do you secure your network against attacks? What is your security policy? What happens to the people who do not follow the security policy? Who is responsible for writing and updating the security policy?

All these questions are valid, and they all deserve answers. Having a network that connects to the Internet via a firewall is only the first step to security; because this book is about first steps, this would be a perfect place to start. You should now know that the security policies form the basis of how firewall rules are determined and then implemented into a production network.

Do you remember the old saying, “No job is ever finished until the paperwork is done?” Well, no security solution is complete until you establish a written narrative of the rules and regulations that govern your organization’s security posture. This written version of your security rules and regulations is known as a security policy. Now, this policy document is different in nature and scope than a security plan, so be sure that you understand what makes a policy unique from every other security document an organization maintains. And just what is it that makes a security policy different from a security plan? Drum-roll please....

PUNISHMENT! That is correct; a security policy includes what is permissible and what will happen to you if you do not live by the law of the land. If you do not follow the rules, you can be

  • Fired or dismissed
  • Demoted
  • Demoted and fined
  • Fired, dismissed, and demoted
  • Demoted, dismissed, and even punked!
  • All the above

All kidding aside, the security policy document spells out in clear language exactly what the regulations and expectations are, who enforces them, and what happens to you if you break them. A security policy is all about the consequences of user actions coupled with audit in the form of AAA usually.

Having said that, how can a firewall be the security policy? Simple—a firewall does what it does by following the rules configured by a network engineer or information security officer (ISO). These rules should perfectly align with a written narrative version found in the security policy document you have on your shelf, next to the box of CDs at the back of the server room or sitting useless in some manager’s office. Grab that old dusty binder and check it out. You should see that the security policy document contains information and a listing of the network rules (refer to Chapter 2). The interesting thing is that all the rules in the policy document form the basis of what you must configure on the firewall.

The configuration rules entered on a firewall should perfectly align with the rules outlined in an organization’s security policy. If you were to examine the firewall’s configuration file, you might see something like Example 7-1, which is a portion of a Cisco Adaptive Security Appliance (ASA) configuration.

Example 7-1 Sample Cisco ASA Firewall Rules

access-list OUTSIDE extended permit tcp any object-group HTTPS-SERVERS eq https

access-list OUTSIDE extended permit tcp any object-group WEB-SERVERS eq www

access-list OUTSIDE extended deny ip host 90.84.x.x any

access-list OUTSIDE extended permit icmp any any time-exceeded

access-list OUTSIDE extended permit icmp any any unreachable

access-list OUTSIDE extended permit icmp any any echo-reply

access-list OUTSIDE extended permit tcp any host 12.238.x.x eq ftp

access-list OUTSIDE extended permit tcp any host 12.238.x.x eq ftp-data

The access-list permit statements in Example 7-1 are most likely in keeping with some security policy statement that dictates what services are allowed, by name, to enter the protected network and the destinations to which those services are allowed to access. Specifically, this example shows the customer having web servers (www-80), secure web servers (https-443), and an FTP-21 server. These permit entries in your firewall’s configuration are your network’s security plan, and the security policy defines what they are and why they are present.

To expand on the firewall to security policy analogy, examine some additional security policy bullet points and how a firewall aligns with them:

  • A security policy outlines what action will be taken in response to circumstances that arise.
  • A security policy document is constantly evolving and changing to meet new security needs.
  • A security policy dictates both acceptable and unacceptable usage parameters.

If you perform a point-by-point comparison of a security policy with a firewall configuration, you see that firewalls act with a written security policy document, as shown in Table 7-1.

Table 7-1 Comparing Security Policies and Firewall Configurations

Security Policy

Firewall Configuration

Ability to respond to circumstances

Yes

Yes

Constantly evolving

Yes

Yes

Dictates behavior

Yes

Yes

The intention of this section is not to convince you that a firewall is a replacement for a security policy document, but to get you thinking about security as an all-encompassing philosophy of plans, policies, and security devices. You must put a great deal of thought into a complete solution—not simply rely on a single aspect to protect your network. When you are ready to plan your firewall’s configuration and develop the rules permitting or denying traffic, you should use your security policy as the starting point. Firewalls are the physical and logical manifestations of your security policy.

3. We Do Not Have a Security Policy | Next Section Previous Section

Cisco Press Promotional Mailings & Special Offers

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

Overview

Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press 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.

Surveys

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.

Newsletters

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

Security

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

Children

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

Marketing

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.

Choice/Opt-out

Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. 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.ciscopress.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.

Links

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