Physical Security

Physical security is an important topic for businesses dealing with the security of information systems. Businesses are responsible for securing their profitability, which requires a combination of several aspects: They need to secure employees, product inventory, trade secrets, and strategy information. These and other important assets affect the profitability of a company and its future survival. Companies therefore perform many activities to attempt to provide physical security-locking doors, installing alarm systems, using safes, posting security guards, setting access controls, and more.

Most companies today have committed a large amount of effort into network security and information systems security. In this chapter, you will learn about how these two security efforts are linked, and you'll learn several methods by which companies can minimize their exposure to physical security events that can diminish their network security.

The Security Problem

The problem that faces professionals charged with securing a company's network can be stated rather simply: Physical access negates all other security measures. No matter how impenetrable the firewall and intrusion detection system (IDS), if an attacker can find a way to walk up to and touch a server, he can break into it. The more remarkable thing is that gaining physical access to a number of machines is not that difficult.

Consider that most network security measures are, from necessity, directed at protecting a company from the Internet. This fact results in a lot of companies allowing any kind of traffic on the local area network (LAN). So if an attacker attempts to gain access to a server over the Internet and fails, he may be able to gain physical access to the receptionist's machine, and by quickly compromising it, he can use it as a remotely controlled zombie to attack what he is really after. Physically securing information assets doesn't mean just the servers; it means protecting the physical access to all the organization's computers and its entire network infrastructure.

Physical access to a corporation's systems can allow an attacker to perform a number of interesting activities, starting with simply plugging into an open Ethernet jack. The advent of handheld devices with the ability to run operating systems with full networking support has made this attack scenario even more feasible. Prior to handheld devices, the attacker would have to work in a secluded area with dedicated access to the Ethernet for a time. The attacker would sit down with a laptop and run a variety of tools against the network, and working internally typically put the attacker behind the firewall and IDS. Today's capable PDAs can assist these efforts by allowing attackers to place the small device onto the network to act as a wireless bridge. The attacker can then use a laptop to attack a network remotely via the bridge from outside the building. If power is available near the Ethernet jack, this type of attack can also be accomplished with an off-the-shelf access point. The attacker's only challenge is finding an Ethernet jack that isn't covered by furniture or some other obstruction.

Drive imaging is the process of copying the entire contents of a hard drive to a single file on a different media. This process is often used by people who perform forensic investigations of computers. Typically, a bootable media is used to start the computer and load the drive imaging software. This software is designed to make a bit-by-bit copy of the hard drive to a file on another media, usually another hard drive or CD-R/ DVD-R media. Drive imaging is used in investigations to make an exact copy that can be observed and taken apart, while keeping the original exactly as it was for evidence purposes.

From an attacker's perspective, drive imaging software is useful because it pulls all information from a computer's hard drive while still leaving the machine in its original state. The information contains every bit of data that was on this computer: any locally stored documents, locally stored e-mails, and every other piece of information that the hard drive contained. This data could be very valuable if the machine held sensitive information about the company.

Physical access is the most common way of imaging a drive, and the biggest benefit for the attacker is that drive imaging leaves absolutely no trace of the crime. While you can do very little to prevent drive imaging, you can minimize its impact. The use of encryption even for a few important files will provide protection. Full encryption of the drive will protect all files stored on it. Alternatively, placing files on a centralized file server will keep them from being imaged from an individual machine, but if an attacker is able to image the file server, the data will be copied.

Physical access can negate almost all the security that the network attempts to provide. Considering this, you must determine the level of physical access that attackers might obtain. Of special consideration are persons with authorized access to the building but who are not authorized users of the systems. Janitorial personnel and others have authorized access to many areas, but they do not have authorized system access. An attacker could pose as one of these individuals or attempt to gain access to the facilities through them.

Physical Security Safeguards

While it is difficult, if not impossible, to be totally secure, many steps can be taken to mitigate the risk to information systems from a physical threat. The following sections discuss policies and procedures as well as access control methods.

Walls and Guards

The primary defense against a majority of physical attacks is the barriers between the assets and a potential attacker-walls and doors. Some organizations also employ full or part-time private security staff to attempt to protect their assets. These barriers provide the foundation upon which all other security initiatives are based, but the security must be designed carefully, as an attacker has to find only a single gap to gain access. Walls may have been one of the first inventions of man. Once he learned to use natural obstacles such as mountains to separate him from his enemy, he next learned to build his own mountain for the same purpose. Hadrian's Wall in England, the Great Wall of China, and the Berlin Wall are all famous examples of such basic physical defenses.

In the case of information assets, as a general rule the most valuable assets are contained on company servers. To protect the physical servers, you must look in all directions: Doors and windows should be safeguarded and a minimum number of each should be used in a server room. Less obvious entry points should also be considered: Is a drop ceiling used in the server room? Do the interior walls extend to the actual roof, raised floors, or crawlspaces? Access to the server room should be limited to the people who need access, not to all employees of the organization. If you are going to use a wall to protect an asset, make sure no obvious holes appear in that wall.

Security personnel can be helpful in securing information assets, but proper protection must be provided. Security guards are typically not computer security experts, so they need to be educated about network security as well as physical security involving users. They are the company's eyes and ears for suspicious activity, so the network security department needs to train them to notice suspicious network activity as well. Multiple extensions ringing in sequence during the night, computers rebooting all at once, or strange people parked in the parking lot with laptop computers are all indicators of a network attack that might be missed. Many traditional physical security tools such as access controls and CCTV camera systems are transitioning from closed hardwired systems to Ethernet- and IP-based systems. This transition opens up the devices to network attacks traditionally performed on computers. With physical security systems being implemented using the IP network, everyone in physical security must become smarter about network security.

Policies and Procedures

A policy's effectiveness depends on the culture of an organization, so all of the policies mentioned here should be followed up by functional procedures that are designed to implement them. Physical security policies and procedures relate to two distinct areas: those that affect the computers themselves and those that affect users.

To mitigate the risk to computers, physical security needs to be extended to the computers themselves. To combat the threat of boot disks, the simplest answer is to remove or disable floppy drives from all desktop systems that do not require them. The continued advance of hard drive capacity has pushed file sizes beyond what floppies can typically hold. LANs with constant Internet connectivity have made network services the focus of how files are moved and distributed. These two factors have reduced floppy usage to the point where computer manufacturers are making floppy drives accessory options instead of standard features. The second boot device to consider is the CD-ROM/DVD-ROM drive. This device can probably also be removed from or disabled on a number of machines. A DVD can not only be used as a boot device, but it can be exploited via the autorun feature that some operating systems support. Autorun was designed as a convenience for users, so that when a CD containing an application is inserted, the computer will instantly prompt for input versus having to explore the CD filesystem and find the executable file. Unfortunately, since the autorun file runs an executable, it can be programmed to do anything an attacker wants. If autorun is programmed maliciously, it could run an executable that installs malicious code that could allow an attacker to later gain remote control of the machine.

To prevent an attacker from editing the boot order, BIOS passwords should be set. These passwords should be unique to the machine and, if possible, complex, using multiple uppercase and lowercase characters as well as numerics. Considering how often these passwords will be used, it is a good idea to list them all in an encrypted file so that a master passphrase will provide access to them.

The most interesting of these, for security purposes, are the USB flash memory- based storage devices. USB drive keys, which are basically flash memory with a USB interface in a device about the size of your thumb, provide a way to move files easily from computer to computer. When plugged into a USB port, these devices auto-mount and behave like any other drive attached to the computer. Their small size and relatively large capacity, coupled with instant read-write ability, present security problems.

They can easily be used by an individual with malicious intent to conceal the removal of files or data from the building or to bring malicious files into the building and onto the company network.

In addition, well-intentioned users could accidentally introduce malicious code from USB devices by using them on an infected home machine and then bringing the infected device to the office, allowing the malware to bypass perimeter protections and possibly infect the organization. If USB devices are allowed, aggressive virus scanning should be implemented throughout the organization. The devices can be disallowed via Active Directory settings or with a Windows registry key entry. They could also be disallowed by unloading and disabling the USB drivers from user's machines, which will stop all USB devices from working-however, doing this can create more trouble if users have USB keyboards and mice. Editing the registry key is probably the most effective solution for users who are not authorized to use these devices. Users who do have authorization for USB drives must be educated about the potential dangers of their use.

Users should be briefed on the proper departments or personnel to contact when they suspect a security violation. Users can perform one of the most simple, yet important, information security tasks: locking a workstation immediately before they step away from it. While a locking screensaver is a good policy, setting it to less than 15 minutes is often counter-productive to active use on the job. An attacker only needs to be lucky enough to catch a machine that has been left alone for 5 minutes. It is also important to know about workers typically overlooked in the organization. New hires should undergo a background check before being given access to network resources. This policy should also apply to all personnel who will have unescorted physical access to the facility, including janitorial and maintenance workers.

Access Controls and Monitoring

Access control means control of doors and entry points. The design and construction of all types of access control systems as well as the physical barriers to which they are most complementary are fully discussed in other texts. Here, we explore a few important points to help you safeguard the information infrastructure, especially where it meets with the physical access control system. This section talks about layered access systems, as well as electronic door control systems. It also discusses closed circuit television (CCTV) systems and the implications of different CCTV system types.

Locks have been discussed as a primary element of security. Although locks have been used for hundreds of years, their design has not changed much: a metal "token" is used to align pins in a mechanical device. As all mechanical devices have tolerances, it is possible to sneak-through these tolerances by "picking" the lock.


A mantrap door arrangement can prevent unauthorized people from following authorized users through an access controlled door, which is also known as "tailgating."

Layered access is an important concept in security. It is often mentioned in conversations about network security perimeters, but in this guide it relates to the concept of physical security perimeters. To help prevent an attacker from gaining access to important assets, these assets should be placed inside multiple perimeters. Servers should be placed in a separate secure area, ideally with a separate authentication mechanism. For example, if an organization has an electronic door control system using contactless access cards, a combination of the card and a separate PIN code would be required to open the door to the server room. Access to the server room should be limited to staff with a legitimate need to work on the servers. To layer the protection, the area surrounding the server room should also be limited to people who need to work in that area.

Many organizations use electronic access control systems to control the opening of doors. Doorways are electronically controlled via electronic door strikes and magnetic locks. These devices rely on an electronic signal from the control panel to release the mechanism that keeps the door closed. These devices are integrated into an access control system that controls and logs entry into all the doors connected to it, typically through the use of access tokens. Security is improved by having a centralized system that can instantly grant or refuse access based upon a token that is given to the user. This kind of system also logs user access, providing non-repudiation of a specific user's presence in a controlled environment. The system will allow logging of personnel entry, auditing of personnel movements, and real-time monitoring of the access controls.

One caution about these kinds of systems is that they usually work with a software package that runs on a computer, and as such this computer should not be attached to the company network. While attaching it to the network can allow easy administration, the last thing you want is for an attacker to have control of the system that allows physical access to your facility. With this control, an attacker could input the ID of a badge that she owns, allowing full legitimate access to an area the system controls. Another problem with such a system is that it logs only the person who initially used the card to open the door-so no logs exist for doors that are propped open to allow others access, or of people "tailgating" through a door opened with a card. The implementation of a mantrap is one way to combat this function. A mantrap comprises two doors closely spaced that require the user to card through one and then the other sequentially. Mantraps make it nearly impossible to trail through a doorway undetected-if you happen to catch the first door, you will be trapped in by the second door.

CCTVs are similar to the door control systems-they can be very effective, but how they are implemented is an important consideration. The use of CCTV cameras for surveillance purposes dates back to at least 1961, when the London Transport train station installed cameras. The development of smaller camera components and lower costs has caused a boon in the CCTV industry since then.

Environmental Controls

While the confidentiality of information is important, so is its availability. Sophisticated environmental controls are needed for current data centers. Fire suppression is also an important consideration when dealing with information systems.

Heating ventilating and air conditioning (HVAC) systems are critical for keeping data centers cool, because typical servers put out between 1000 and 2000 BTUs of heat. Enough servers in a confined area will create conditions too hot for the machines to continue to operate. The failure of HVAC systems for any reason is cause for concern.

Properly securing these systems is important in helping prevent an attacker from performing a physical DoS attack on your servers. Fire suppression systems should be specialized for the data center. Standard sprinkler-based systems are not optimal for data centers because water will ruin large electrical infrastructures and most integrated circuit-based devices-that is, computers. Gas-based systems are a good alternative, though they also carry special concerns. Halon was used for many years, and any existing installations may still have it for fire suppression in data centers. Halon displaces oxygen, and any people caught in the gas when the system goes off will need a breathing apparatus to survive. Halon is being replaced with other gas-based suppression systems, such as argon and nitrogen mixing systems or carbon dioxide, but the same danger to people exists, so these systems should be carefully implemented.


Authentication is the process by which a user proves that she is who she says she is. Authentication is performed to allow or deny a person access to a physical space. The heart of any access control system is to allow access to authorized users and to make sure access is denied to unauthorized people. Authentication is required because many companies have grown so large that not every employee knows every other employee, so it can be difficult to tell by sight who is supposed to be where. Electronic access control systems were spawned from the need to have more logging and control than provided by the older method of metallic keys. Most electronic systems currently use a token-based card that if passed near a reader, and if you have permission from the system, will unlock the door strike and let you pass into the area. Newer technology attempts to make the authentication process easier and more secure.

Access Tokens

Access tokens are defined as "something you have." An access token is a physical object that identifies specific access rights, and in authentication falls into the "something you have" factor. Your house key, for example, is a basic physical access token that allows you access into your home. Although keys have been used to unlock devices for centuries, they do have several limitations. Keys are paired exclusively with a lock or a set of locks, and they are not easily changed. It is easy to add an authorized user by giving the user a copy of the key, but it is far more difficult to give that user selective access unless that specified area is already set up as a separate key. It is also difficult to take access away from a single key or key holder, which usually requires a rekey of the whole system.

The primary drawback of token-based authentication is that only the token is being authenticated. Therefore, the theft of the token could grant anyone who possessed the token access to what the system protects. The risk of theft of the token can be offset by the use of multiple-factor authentication. One of the ways that people have tried to achieve multiple-factor authentication is to add a biometric factor to the system.


Biometrics uses the measurements of certain biological factors to identify one specific person from others. These factors are based on parts of the human body that are unique. The most well-known of these unique biological factors is the fingerprint. However, many others can be used-for instance, the retina or iris of the eye, the geometry of the hand, and the geometry of the face. When these are used for authentication, there is a two part process, enrollment and then authentication. During enrollment, a computer takes the image of the biological factor and reduces it to a I numeric value. When the user attempts to authenticate, this feature is scanned by the reader, and the computer compares the numeric I value being read to the one stored in the database. If they match, access is allowed. Since these physical factors are unique, theoretically

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only the actual authorized person would be allowed access.

A major concern with biometrics is that if someone is able to steal the uniqueness factor that the machine scans-your fingerprint from a glass, for example-and is able to reproduce that factor in a substance that fools the scanner, that person now has your access privileges. This idea is compounded by the fact that it is impossible for you to change your fingerprint if it gets stolen. It is easy to replace a lost or stolen token and delete the missing one from the system, but it is far more difficult to replace a human hand. Another problem with biometrics is that parts of the human body can change. A human face can change, through scarring, weight loss or gain, or surgery. A fingerprint can be changed through damage to the fingers. Eye retinas can be affected by some types of diabetes or pregnancy. All of these changes force the biometric system to allow a higher tolerance for variance in the biometric being read. This has led the way for high-security installations to move toward multiple-factor authentication.

Multiple-factor Authentication

Multiple-factor authentication is simply the combination of two or more types of authentication. Three broad categories of authentication can be used: what you are (for example, biometrics), what you have (for instance, tokens), and what you know (passwords and other information). Two-factor authentication combines any two of these before granting access. An example would be a card reader that then turns on a fingerprint scanner-if your fingerprint matches the one on file for the card, you are granted access. Three-factor authentication would combine all three types, such as a smart card reader that asks for a PIN before enabling a retina scanner. If all three correspond to a valid user in the computer database, access is granted.

Multiple-factor authentication methods greatly enhance security by making it very difficult for an attacker to obtain all the correct materials for authentication. They also protect against the risk of stolen tokens, as the attacker must have the correct biometric, password, or both. More important, it enhances the security of biometric systems. Multiple-factor authentication does this by protecting against a stolen biometric. Changing the token makes the biometric useless unless the attacker can steal the new token. It also reduces false positives by trying to match the supplied biometric with the one that is associated with the supplied token. This prevents the computer from seeking a match using the entire database of biometrics. Using multiple factors is one of the best ways to ensure proper authentication and access control.