Home > Articles > Security > Network Security

This chapter is from the book

Sample Configurations

The following subsections present three situations that build on each other as the network and the needs of the enterprise change.

SMTP Content Security

The Situation

Your company wants to gradually roll in Content Security throughout its enterprise. One of the most prevalent sources of viruses has been incoming e-mail, so the managers decide to start with e-mail. Both incoming and outgoing e-mail will be scanned. HTTP and FTP traffic will eventually be scanned. (This functionality will be added in the next two situations.) The CVP and UFP servers are sitting in the DMZ. Figure 9.33 shows the network diagram for this company.

09fig33.gifFigure 9.33. Network diagram for sample configuration

The Goals

  • The Web server in the DMZ will be accessible via HTTP from anywhere.

  • The e-mail server in the DMZ will be accessible via SMTP from anywhere and can send e-mail to anywhere on the Internet.

  • The e-mail server in the DMZ can talk to the internal e-mail server via SMTP and vice versa. In either case, all traffic will be scanned for viruses.

  • Clients on the internal network can talk to any host via HTTP and FTP.

  • The UFP and CVP servers need to access their respective vendors' Web sites via HTTP to download updates (www.cvp-vendor.com and www.ufp-vendor.com).

  • All other traffic should be denied.

The Checklist

  • Create the necessary network objects.

  • Ensure that the SMTP Security Server is enabled in $FWDIR/conf/fwauthd.conf.

  • Create two SMTP resources to handle inbound and outbound e-mail between the internal and the DMZ e-mail servers and scan viruses.

  • Create the appropriate rule(s) in the rulebase.

  • Verify and install the policy.

The Implementation

The proper line for the SMTP Security Server in $FWDIR/conf/fwauthd.conf looks like this (with no comment character, #, at the beginning of the line):

25              fwssd            in.asmtpd       wait    0

On most systems, this line is enabled by default, but it never hurts to make sure that this line exists and is not commented out.

The two resources then need to be created. The first resource is for e-mail coming from the DMZ-based e-mail server that forwards it to the internal e-mail server. All incoming e-mail should be forwarded to the internal SMTP server. Any errors generated should go to the DMZ-based e-mail server so they can be sent to the sender. Figure 9.34 shows how this resource looks.

09fig34.gifFigure 9.34. Incoming e-mail SMTP resource, General tab

You can leave the Match tab blank if you want because the internal and DMZ-based e-mail servers can do address checking on their own. For this example, let's leave the Action1 tab alone as well because there is no need to do any address rewriting.

In the Action2 tab, shown in Figure 9.35, strip out all messages of MIME type message/partial because it is used for sending a file across more than one message. This makes it difficult, if not impossible, to scan the file for viruses. The default message size should also be increased from 1,000KB to 5,000KB as a courtesy to users. However, I generally do not recommend sending large files by e-mail because e-mailed files are actually bigger than they are if downloaded from an FTP or HTTP server. In order to e-mail binary files, they must be turned into a nonbinary format, which increases the overall file size.

09fig35.gifFigure 9.35. Incoming e-mail SMTP resource, Action2 tab

Configure the CVP tab as shown in Figure 9.36.

09fig36.gifFigure 9.36. Incoming e-mail SMTP resource, CVP tab

Then create the outbound resource as shown in Figure 9.37.

09fig37.gifFigure 9.37. Outgoing e-mail SMTP resource, General tab

It might also be nice to strip out the "received" lines of messages being sent from the inside to the outside. This is done on the Action1 tab (see Figure 9.38).

09fig38.gifFigure 9.38. Outgoing e-mail SMTP resource, Action1 tab

The Action2 and CVP tabs should look identical to what was used for the inbound resource. In the end, the rulebase should look similar to the one shown in Figure 9.39.

09fig39.gifFigure 9.39. Rulebase for SMTP Security Server sample configuration

Once this configuration is set up, verify and install the security policy.

FTP Content Security

The Situation

The next step in the company's Content Security plan is to turn on Content Security for FTP. Additionally, the company wants to use the FTP Security Server to allow people to upload files only to a specific directory on the Web server.

The Goal

  • Create and implement resources to perform the necessary Content Security for FTP.

The Checklist

  • Ensure that the FTP Security Server is enabled in $FWDIR/conf/fwauthd.conf.

  • Create an FTP resource to scan for viruses.

  • Create an FTP resource to scan for viruses and restrict access to a specific directory on the Web server.

  • Create an FTP resource to allow people to download files from the Web server.

  • Modify the rulebase to use these FTP resources.

  • Verify and install the policy.

The Implementation

The proper line for the FTP Security Server in $FWDIR/conf/fwauthd.conf looks like this (with no comment character, #, at the beginning of the line):

25              fwssd            in.aftpd       wait    0

On most systems, this line is enabled by default, but it never hurts to check.

The first resource you need to create is the more general one to match everything and allow users to upload and download as they please, with the exception that all file transfers will be scanned for viruses. This configuration is shown in Figure 9.40.

09fig40.gifFigure 9.40. FTP scan resource, General tab

The Match tab should match all actions and paths as shown in Figure 9.41.

09fig41.gifFigure 9.41. FTP scan resource, Match tab

The CVP tab, of course, should scan for viruses (see Figure 9.42).

09fig42.gifFigure 9.42. FTP scan resource, CVP tab

The Web server upload resource needs to match a specific path. Use the Match tab as shown in Figure 9.43.

09fig43.gifFigure 9.43. FTP Web server upload resource, Match tab

You are going to virus scan anything uploaded to make sure you do not pass any viruses to the outside world. The CVP tab for this configuration is shown in Figure 9.42.

Finally, you need to create a resource to allow the internal users to download from the Web server. Because you are not terribly concerned about where on that server users download from, the Match tab should match any path for GET commands, as shown in Figure 9.44.

09fig44.gifFigure 9.44. FTP Web server download resource, Match tab

Once the resources are created, you can modify the existing policy to use them. The rulebase should look similar to the one shown in Figure 9.45. Rules 6, 7, and 8 were added to the previous rulebase (pushing the original Rules 6 through 9 shown in Figure 9.39 into their new positions as Rules 9 through 12 in Figure 9.45).

09fig45.gifFigure 9.45. Rulebase with SMTP and FTP Security Server sample configuration

After updating the rulebase, verify and install the security policy.

HTTP Content Security

The Situation

The final step in implementing the company's Content Security plan is to implement both virus scanning and URL filtering for HTTP traffic.

The Goals

  • Create and implement a resource for URL filtering and Content Security for HTTP.

  • Make sure Content Security is not performed for internal users accessing the DMZ.

The Checklist

  • Ensure that the HTTP Security Server is enabled in $FWDIR/conf/fwauthd.conf.

  • Create a resource of type URI for URL filtering for HTTP.

  • Create a resource of type URI that matches all URLs and does virus scanning.

  • Modify the rulebase to use the HTTP resources.

  • Verify and install the policy.

The Implementation

The proper line for the HTTP Security Server in $FWDIR/conf/fwauthd.conf looks like this (with no comment character, #, at the beginning of the line):

25              fwssd            in.ahttpd       wait    0

On most systems, this line is enabled by default, but it never hurts to check.

You first need to create a resource to filter URLs, as shown in Figure 9.46.

09fig46.gifFigure 9.46. URI-filtering resource, General tab

The Match tab should match the categories of Web sites you do not want the employees to view (see Figure 9.47).

09fig47.gifFigure 9.47. URI-filtering resource, Match tab

Configure the settings on the Action tab (see Figure 9.48) to redirect rejected URLs to a policy page.

09fig48.gifFigure 9.48. URI-filtering resource, Action tab

This completes the setup for the URL filtering resource. You then need to do virus scanning on any URL that is accepted. A second resource must be created, as shown in Figure 9.49.

09fig49.gifFigure 9.49. HTTP virus-scanning resource, General tab

The Match tab settings should match all URLs, and the CVP tab settings should filter viruses (see Figures 9.50 and 9.51, respectively).

09fig50.gifFigure 9.50. HTTP virus-scanning resource, Match tab

09fig51.gifFigure 9.51. HTTP virus-scanning resource, CVP tab

You then implement these resources in the rulebase, as shown in Figure 9.52. Rule 9 in the previous rulebase was replaced by a different Rule 9, and a new rule was added in the Rule 10 position, shifting down the remaining rules.

09fig52.gifFigure 9.52. Rulebase with SMTP, FTP, and HTTP Security Servers sample configuration

After making these changes, verify and install the policy.


Rule 1 also matches internal users' attempts to access the Web server on the DMZ.

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