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This chapter is from the book

This chapter is from the book

3.2: Understanding Media Security

The essence of a network is that a series of computers are connected in some fashion to one another and transmitting information across some type of media. Although you might have secured your computers and other devices to the strongest extent possible, attackers might still be able to access information as it flows across the wires or from removable media such as CDs, tapes, and disks and use this information for their benefit or for pursuing more potent attacks on your network.

Exercise 3.2.1: Understanding Media Security Concepts

Networking cable types whose security concerns you need to be familiar with include coax (thinnet or 10Base-2 and thicknet or 10Base-5), twisted pair (UTP and STP), and fiber optic. In this exercise, you research the security concerns of these networking media.

  1. From a Web browser, connect to the Internet and navigate to http://www.enterasys.com/support/techtips/tk0399-9.html. This document provides a background of the specifications of the various networking media, which should all be familiar to anyone who has taken the Network+ exam.

  2. Continue to http://c0vertl.tripod.com/text/ethernet.htm and note some problems that exist with the various types of networking cable. Which troubleshooting device do the authors claim can detect tapping of a network cable?

  3. Continue to http://www.puredata.com/supports/faqs/fiber/faqs.html and find out why eavesdropping of fiber-based networks is virtually impossible.

  4. Note the table comparing characteristics of network media at http://website.lineone.net/~paulcon/70-58-2.html. Which type of media is most subject to eavesdropping?

  5. You might want to conduct a search on Google or Yahoo! for additional articles that relate to security concerns of Ethernet media, but be forewarned that not much relevant material is present.

In addition to these sources, review the material provided in the Exam Cram 2 and the Training Guide for the Security+ exam for additional information on networking media security concerns. (See the "Need to Know More?" section at the end of this chapter.)


Keep in mind other properties of network media when it comes to assessing security of the different media types. For example, cabling located in a location subject to electromagnetic interference should be shielded in some manner. STP or fiber optic cable is more suitable to such a location than UTP cable such as standard 10Base-T or 100Base-T installations.

Exercise 3.2.2: Securing Removable Media

Unauthorized users who can remove disks or tapes from a network can steal information from the network; they can also insert disks containing viruses, Trojan horses, sniffers, or other unauthorized software to facilitate other attacks. In this exercise, you look at some of the concerns of removable media security:

  1. Rick Cook discusses the security of backup tapes at http://searchstorage.techtarget.com/tip/1,289483,sid5_gci756807,00.html. What method does he suggest for improving the security of these tapes?

  2. A good source for information on data security management is http://www.degaussing.net/security-issues-in-data-facility-management.html. They review degaussing of magnetic media, including tapes and hard disks, and offer a large number of links to additional sources. Study this reference and enumerate all the issues they discuss related to security of data stored on tapes and disks. Also locate as many reasons as possible for performing complete data erasure on tapes and disks that are no longer required.

  3. Threats to data stored on removable media can come from within the company as well as outside. Note some of the precautions you should observe when planning backup strategies in http://www.nss.co.uk/WhitePapers/data_storage_mment/data_storage_mment.htm. Follow the two "Security" links in the article's table of contents. What is a potential loophole associated with an unattended backup taking place at a user's desktop? What is a potential security breach associated with members of the Backup Operators group also being able to restore data?

  4. Thanks to readily available hardware and software solutions, recordable CDs can present a security problem because it is easy to copy data to a CD and remove it from the premises. Data Link Associates sells a CD/optical media eraser, which they claim can erase all types of CDs. For information on this product, go to http://www.datalinksales.com/degaussers/1200.htm. A hand-cranked device described at http://www.datalinksales.com/degaussers/shredder434355.htm completely destroys CDs and DVDs.

  5. David White discusses systems security at http://www.dbmsmag.com/9711d13.html. His article includes smart card and PCMCIA card security concerns. What is one way in which an unauthorized user can obtain information from a smart card? He also discusses topics of interest related to several other Security+ objectives.

  6. Stephen Wilson discusses smart card and hardware key security at http://www.sans.org/rr/papers/20/763.pdf. We discuss certificate and hardware key security in Chapter 4. What are some of the security features that Wilson mentions? What is the biggest limitation regarding the use of smart cards, and what solution does he advocate for this limitation?

Exercise 3.2.3: Using the Encrypting File System to Encrypt Data in Windows 2000 Server

Starting with Windows 2000, Microsoft made available an easily implemented system of encrypting data on a hard disk with the Encrypting File System (EFS). This method of encryption is especially useful for portable computers that are subject to loss or theft and prevents data from being copied after removing the disk to another computer or by an intruder who does not know the username or password under which the data was encrypted. In this exercise, you encrypt a test file and then attempt to access it as an unauthorized user. Perform this exercise on a computer running Windows 2000 Server. You can also do this exercise on a computer running Windows XP Professional or Windows Server 2003. In any case, the hard disk must be formatted with the NTFS file system:

  1. Log on to the computer running Windows 2000 Server as an administrator.

  2. Open My Computer and navigate to the C: drive.

  3. Create a new folder named Encrypt.

  4. Right-click this folder and choose Properties.

  5. On the General tab of the Encrypt Properties dialog box, click Advanced.

  6. In the Advanced Attributes dialog box that opens, select the Encrypt Contents to Secure Data check box (see Figure 3.8), and then click OK.

  7. Figure 3.8Figure 3.8 Encrypt a folder in Windows 2000 Server.

  8. Click Apply to apply the change.

  9. NOTE

    If you are using Windows XP Professional or Windows Server 2003, you must select the Security tab of the Encrypt Properties dialog box, select the Users entry, select the Full Control permission under the Allow column, and then click OK. Granting this permission is necessary so that you can distinguish the effect of data encryption from that of the application of NTFS permissions, as we discussed in Chapter 1.

  10. Open the Encrypt folder and create a text document by selecting File, New, Text Document and then typing Text1.txt as the filename.

  11. Open this document and type something in the body of the document that identifies the document. Save the document and close Notepad.

  12. Log off and log on as the User1 user you created in Chapter 1.

  13. Navigate to and attempt to open the text document in the C:\Encrypt folder. What happens? You receive an "Access is denied" message because the document was encrypted by the administrator. Any user can create an encrypted document according to permissions specified on the folder in which the document is created.

  14. To prove this point, repeat Steps 8 and 9 to create another document as the User1 user. Then log off and log back on as the administrator and try to open this document. You receive the same message because this document was encrypted by the User1 user. EFS provides this second level of security that is valuable in situations where the computer might be vulnerable to theft or other unauthorized access.

What Did I Just Learn?

Now that you have looked at media concerns, let's take a moment to review all the critical items you've experienced in this lab:

  • You need to keep your network cabling media secure from intrusions such as eavesdropping by means of wiretapping, which can occur on coaxial and twisted-pair networking configurations.

  • Fiber optic cable is more difficult to compromise than coaxial or twisted-pair networking media. However, it is more expensive and difficult to work with. Its usage is mainly in places where physical security is difficult to achieve or where the need for large bandwidth or freedom from electromagnetic interference is required.

  • Removable media such as tapes, CDs, disks, flash cards, and smart cards can present security problems because of the ease of removal from work premises. The same is true with regard to hard disks, although these take more time to remove except in hot-swap configurations.

  • EFS in Windows 2000/XP/2003 provides an additional layer of data security that is especially valuable in situations where theft or loss of portable computers is possible.

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