Home > Articles > Security > Network Security

  • Print
  • + Share This
This chapter is from the book

Security Principles: Detection

Detection lies at the heart of the NSM operation, but it is not the ultimate goal of the NSM process. Ideally, the NSM operation will detect an intrusion and guide incident response activities prior to incident discovery by outside means. Although it is embarrassing for an organization to learn of compromise by getting a call from a downstream victim or customer whose credit card number was stolen, these are still legitimate means of detecting intrusions.

As mentioned in Chapter 1, many intruders are smart and unpredictable. This means that people, processes, and products designed to detect intrusions are bound to fail, just as prevention inevitably fails. If both prevention and detection will surely fail, what hope is there for the security-minded enterprise?

NSM's key insight is the need to collect data that describes the network environment to the greatest extent possible. By keeping a record of the maximum amount of network activity allowed by policy and collection hardware, analysts buy themselves the greatest likelihood of understanding the extent of intrusions. Consider a connectionless back door that uses packets with PSH and ACK flags and certain other header elements to transmit information. Detecting this sort of covert channel can be extremely difficult until you know what to monitor. When an organization implements NSM principles, it has a higher chance of not only detecting that back door but also keeping a record of its activities should detection happen later in the incident scenario. The following principles augment this key NSM insight.

Intruders Who Can Communicate with Victims Can Be Detected

Intrusions are not magic, although it is wise to remember Arthur C. Clarke's Third Law: "Any sufficiently advanced technology is indistinguishable from magic." [15] Despite media portrayals of hackers as wizards, their ways can be analyzed and understood. While reading the five phases of compromise in Chapter 1, you surely considered the difficulty and utility of detecting various intruder activities. As Table 1.2 showed, certain phases may be more observable than others. The sophistication of the intruder and the vulnerability of the target set the parameters for the detection process. Because intruders introduce traffic that would not ordinarily exist on a network, their presence can ultimately be detected. This leads to the idea that the closer to normal intruders appear, the more difficult detection will be.

This tenet relates to one of Marcus Ranum's "laws of intrusion detection." Ranum states, "The number of times an uninteresting thing happens is an interesting thing." [16] Consider the number of times per day that an organization resolves the host name "www.google.com." This is an utterly unimpressive activity, given that it relates to the frequency of searches using the Google search engine. For fun, you might log the frequency of these requests. If suddenly the number of requests for www.google.com doubled, the seemingly uninteresting act of resolving a host name takes on a new significance. Perhaps an intruder has installed a back door that communicates using domain name server (DNS) traffic. Alternatively, someone may have discovered a new trick to play with Google, such as a Googlewhack or a Googlefight. [17]

Detection through Sampling Is Better Than No Detection

Security professionals tend to have an all-or-nothing attitude toward security. It may be the result of their ties to computer science, where answers are expressed in binary terms of on or off, 1 or 0. This attitude takes operational form when these people make monitoring decisions. If they can't figure out a way to see everything, they choose to see nothing. They might make some of the following statements.

  • "I run a fractional OC-3 passing data at 75 Mbps. Forget watching it—I'll drop too many packets."

  • "I've got a switched local area network whose aggregated bandwidth far exceeds the capacity of any SPAN port. Since I can't mirror all of the switch's traffic on the SPAN port, I'm not going to monitor any of it."

  • "My e-commerce Web server handles thousands of transactions per second. I can't possibly record them all, so I'll ignore everything."

This attitude is self-defeating. Sampling can and should be used in environments where seeing everything is not possible. In each of the scenarios above, analyzing a sample of the traffic gives a higher probability of proactive intrusion detection than ignoring the problem does. Some products explicitly support this idea. A Symantec engineer told me that his company's ManHunt IDS can work with switches to dynamically reconfigure the ports mirrored on a Cisco switch's SPAN port. This allows the ManHunt IDS to perform intrusion detection through sampling.

Detection through Traffic Analysis Is Better Than No Detection

Related to the idea of sampling is the concept of traffic analysis. Traffic analysis is the examination of communications to identify parties, timing characteristics, and other meta-data, without access to the content of those communications. At its most basic, traffic analysis is concerned with who's talking, for how long, and when. [18] Traffic analysis has been a mainstay of the SIGINT community throughout the last century and continues to be used today. (SIGINT is intelligence based on the collection and analysis of adversary communications to discover patterns, content, and parties of interest.)

Traffic analysis is the answer to those who claim encryption has rendered intrusion detection obsolete. Critics claim, "Encryption of my SSL-enabled Web server prevents me from seeing session contents. Forget monitoring it—I can't read the application data." While encryption will obfuscate the content of packets in several phases of compromise, analysts can observe the parties to those phases. If an analyst sees his or her Web server initiate a TFTP session outbound to a system in Russia, is it necessary to know anything more to identify a compromise? This book addresses traffic analysis in the context of collecting session data in Chapters 7 and 15.

  • + Share This
  • 🔖 Save To Your Account

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.

Overview


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.

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@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.

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 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.

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