The term hacker has a double meaning. The honorable interpretation of hacker refers to a computer programmer who is able to create usable computer programs where none previously existed. In this Study Guide, we refer to the dishonorable interpretation of a hacker—an undesirable criminal. The criminal hacker focuses on a desire to break in, take over, and damage or discredit legitimate computer processing. The first goal of hacking is to exceed the authorized level of system privileges. This is why it is necessary to monitor systems and take swift action against any individual who attempts to gain a higher level of access. Hackers may be internal or external to the organization. Attempts to gain unauthorized access within the organization should be dealt with by using the highest level of severity, including immediate termination of employment.

The term cracker is a variation of hacker, with the analogy equal to a safe cracker. Some individuals use the term cracker in an attempt to differentiate from the honorable computer programmer definition of hacker. The criminal cracker and criminal hacker terms are used interchangeably. Crackers attempt to illegally or unethically break into a system without authorization.

A number of specialized programs exist for the purpose of bypassing security controls. Many hacker tools began as well-intentioned tools for system administration. The argument would be the same if we were discussing a carpenter's hammer. A carpenter's hammer used for the right purpose is a constructive tool. The same tool is a weapon if used for a nefarious purpose. A script kiddy is an individual who executes computer scripts and programs written by others. Their motive is to hack a computer by using someone else's software. Examples include password decryption programs and automated access utilities. Several years ago, a login utility was created for Microsoft users to get push-button access into a Novell server. This nifty utility was released worldwide before it was recognized that the utility bypassed Novell security. The utility was nicknamed Red Button and became immensely popular with script kiddies. Internal controls must be put in place to restrict the possession or use of administration utilities. Violations should be considered severe and dealt with in the same manner as hacker violations.

There is a reason why the FBI report cited the high volume of internal crimes. A person within the organization has more access and opportunity than anyone else. Few persons would have a better understanding of the security posture and weaknesses. In fact, an employee may be in a position of influence to socially engineer coworkers into ignoring safeguards and alert conditions. This is why it is important to monitor internal employee satisfaction. The great medieval fortresses fell by the betrayal of trusted allies.

The term ethical hacker or white hat is a new definition in computer security. An ethical hacker is one who is authorized to test computer hacks and attacks with the goal of identifying an organization's weakness. Some individuals participate in special training to learn about penetrating computer defenses. This will usually result in one of two outcomes.

In the first outcome, a few of the ethical white-hat technicians will exercise extraordinary restraint and control. The objective of ethical hacking is to exercise hacker techniques only in a highly regimented, totally supervised environment. The white-hat technician will operate from a prewritten test plan, reviewed by internal audit or management oversight. The slightest deviation is grounds for termination. This additional level of control is to protect the organization from error or personal agenda by the white-hat technician.

The second outcome is that a white-hat technician will direct their own efforts. Some individuals will demonstrate great pride in their ability to circumvent required controls. These self-directed hacking techniques create an unacceptable level of risk for multiple reasons including organizational liability. The series of movies about Jason Bourne, The Bourne Identity (2002), The Bourne Supremacy (2004), and The Bourne Ultimatum (2007) illustrate the risk of self-directed activity. After management loses control, there is no way back. These fictional movies are, in part, based on facts from real events.

External persons are referred to as third parties. Third parties include visitors, vendors, consultants, maintenance personnel, and the cleaning crew. These individuals may gain access and knowledge of the internal organization.

The term ignorance is simply defined as the lack of knowledge. An ignorant person may be a party to a crime and not even know it. Even worse, the individual may be committing an offense without realizing the impact of their actions. Management may be guilty of not understanding their current risks and corresponding regulations. The statement "We/I did not know" is the fastest route to a conviction. Every judge will agree that ignorance of the law is not an excuse. Every manager is expected to research the regulations bearing upon their business practice. There is no legal excuse for ignorance or apathy. Fortunately, ignorance can be cured by training. This is the objective of user training for internal controls. By teaching the purpose of internal security controls, the organization can reduce their overall risk.

Passive attacks are characterized by techniques of observation. The intention of a passive attack is to gain additional information before launching an active attack. Three examples of passive attacks are network analysis, traffic analysis, and eavesdropping:

Now let's move on to discuss the active attacks.

Passive attacks tend to be relatively invisible, whereas active attacks are easier to detect. The attacker will proceed to execute an active attack after obtaining sufficient background information. The active attack is designed to execute an act of theft or to cause a disruption in normal computer processing. Following is a list of active attacks:

A variety of other technical attacks may be launched against the computer. A common attack is to send to the computer an impossible request or series of requests that cannot be serviced. These cause the system to overload its CPU, memory, or communication buffers. As a result, the computer crashes. An example is the old Ping of Death command (ping -l 65510), which exceeded the computer's maximum input size for a communication buffer.

The first step in preventing the loss of information assets is to establish administrative controls. Let's begin the discussion on implementing administrative safeguards.

The data owner refers to executives or managers responsible for the data content. The role of the data owner is to do the following:

As an IS auditor, you will review the decisions made by the data owner to evaluate whether the actions were appropriate.

The data user is the business person who benefits from the computerized data. Data users may be internal or external to the organization. For example, some data is delivered for use across the Internet. The role of the data user includes the following tasks:

You will evaluate the effectiveness of management to communicate their controls to the user. The auditor investigates the effectiveness and integration of policies and procedures with the user community. In addition, the auditor determines whether user training has been effectively implemented.

The data custodian is responsible for implementing data storage safeguards and ensuring availability of the data. The custodian's role is to support the business user. If something goes wrong, it is the responsibility of the custodian to deal with this promptly. Sometimes the custodian's role is equivalent to a person holding the bag of snakes at a rattlesnake roundup or the role of a plumber when fixing a clogged drain. The duties of the data custodian include the following:

Now we have identified the information classification and the job roles of owner, user, and custodian. The next step is to identify data retention requirements.

Physical access is a major concern to IT security. As an IS auditor, you need to investigate how access is granted for employees, visitors, vendors, and service personnel. Which of these individuals are escorted and which are left unattended? What is the nature of physical controls and locking doors? Are there any internal barriers to prevent unauthorized access?

The following is a list of the three top concerns regarding physical access:

Administrative procedures are necessary to ensure that access is terminated when an employee leaves the organization. The access of existing employees should also be reviewed on a regular basis. In a poorly managed organization, the employee will be given access to one area and then to additional areas as their jobs change. Unfortunately, this results in a person with more access than their job requires. Access to sensitive areas should be limited to persons who perform a required job function in the same area. If the person is moved out of the area, that access should be terminated. The IS auditor should investigate how the organization terminates access and whether it reviews existing access levels. The concept of least privilege should be enforced. The minimum level of access is granted to perform the required job role.

Incident handling is an administrative process we discussed in Chapter 6, "IT Service Delivery." Physical damage or an unlocked door at the wrong time should initiate the incident-handling process. Auditors will need to investigate how the organization deals with incident handling in regard to security implications.

Auditors need to ask the following questions:

Policies and procedures in security plans are ineffective unless management is monitoring compliance. An effective process of monitoring will detect violations. Better control occurs when activity monitoring is separate from the person or activity performing the work. Self-monitoring is a violation of IT governance controls. The built-in reporting conflict of self-monitoring will seriously question the integrity of the reporting process. Separation of duties applies to people, systems, and violation reporting. The IS auditor needs to investigate how violations are reported to management:

The role of the IS auditor in personnel management is to determine whether appropriate controls are in place to manage the activities of people inside the organization. Now we will move on to physical protection.

Electricity is both an advantage and a hazard. The national fire-protection code requires an emergency power off (EPO) switch to be located near the exit door. The purpose of this switch is to kill power to prevent an individual from being electrocuted. The EPO switch is a red button, which should have a plastic cover to prevent accidental activation. The switch can be wired into the fire-control system for automatic power shutoff if the fire-control system releases water or chemicals to disable a fire.

The uninterruptible power supply (UPS) is an intelligent power monitor coupled with a string of electrical batteries. The UPS constantly monitors electrical power. A UPS can supplement low-voltage conditions by using power stored in the batteries. During a power outage, the UPS will provide a limited amount of battery power to keep the systems running. The duration of this battery power depends on the electrical consumption of the attached equipment. Most UPS units are capable of signaling the computer to automatically shut down before the batteries are completely drained. Larger commercial UPS systems have the ability to signal the electrical standby generator to start.

The standby generator provides auxiliary power whenever commercial power is disrupted. The standby generator can be connected to the UPS for an automated start. The UPS will signal the generator that power is required, and the generator will start warming up. After the generator is warmed up, a transfer circuit will switch the electrical feed from commercial power to the generator power. The UPS will filter the generator power and begin recharging batteries. The standby generator can run for as long as it has fuel. Most standby generators run on diesel fuel or natural gas:

The best way to prevent power outages is to install power leads from two different power substations. It would be extremely expensive to just pay someone to run special power cables. Instead, the location of the building housing the computer room should be selected according to area power grids. Power grids are usually divided along highways. Careful location selection will place your building within a quarter-mile of two power grids. This makes the cost of the dual connection affordable. Dual power leads should approach the building from different directions without sharing the same underground trench. A construction backhoe is extremely effective in destroying underground connections.

The power transfer system, known as a transfer switch, provides the connection between commercial power and UPS battery power in the generator. The transfer switch may be manual or computerized. It is not uncommon for the power transfer switch to fail during a power outage. Therefore, manual power-transfer procedures should be in place. Automated power-transfer switches may not be able to react to a pair of short power failures occurring within the same 30-minute window. After the first power failure, the generator will come online to produce electrical current. After commercial electrical power is restored, the power switch will transfer back to commercial electricity. At the same time, the generator will receive a signal to begin cooling down and finally shut off. If another power outage occurs during the generator cooling period, the power transfer switch will cycle to generator power while the generator is not producing electrical current. This condition may be resolved by increasing the battery capability of the UPS and adjusting generator start and stop times.

Figure 7.5 illustrates the basic electrical power system used for computer installations.

Figure 7.5. Power system overview

The computer installation requires heating, ventilation, and air-conditioning. Electronic equipment performs well in cold conditions; however, magnetic media should not be allowed to freeze. Ventilation is necessary for cooling computer equipment. Physical damage occurs if the computer circuitry sustains extended use at temperatures of 104 degrees or higher. Physical damage will also occur if the internal electronic circuitry exceeds 115 degrees during operation.

Air-conditioning is also used to control humidity. Humidity will control static electricity that could damage electrical circuits. The ideal humidity for a computer room is between 35 percent and 45 percent at 72 degrees. This will reduce the atmospheric conditions that would otherwise create high levels of static electricity.

The data center and records storage area should be equipped for fire, smoke, and heat detection. Unheated areas may need to be monitored for freezing conditions. There are three basic types of fire detectors, using smoke detection, heat detection, or flame detection:

A fire-detection system activates an alarm to initiate human response. A fire-detection system may also activate fire suppression with or without the discharge of water or chemicals.

Fire suppression is the next step after fire detection. A fire-suppression system may be fully automated or mechanical. There are three basic types of fire-suppression systems:

Water is discharged from air-conditioning or cooling systems and usually runs to a drain located under the raised floor. Water-detection systems are necessary under the floor to alert personnel of a clogged drain or plumbing backup. Water-detection sensors also may be placed in the ceiling to detect leakage from pipes in the roof above. It is common for water pipes to be located over a computer room directly above the ceiling tiles or higher floors. Water can even cascade down inside the building from the roof.

Figure 7.9 provides a simple overview of a data processing center and the various environmental control systems.

To minimize risk, the organization should have a policy prohibiting food, liquids, and smoking in the computer facility. Now it is time to discuss safe storage of assets and media records.

Figure 7.9. Typical computer room

The offsite storage facility provides storage for a second copy of vital records and data backup files. The offsite storage facility should be used for safe long-term retention of records. The standard practice is to send backup tapes offsite every day or every other day. The offsite storage location should be a well-designed, secure, bonded facility with 24-hour security. This site must be designed for protection from flood, fire, and theft. The offsite vendor should maintain a low profile without visible markings identifying the contents of the facility to a casual passerby. Most offsite storage facilities provide safe media transport.

Business records and magnetic media should be properly boxed for transit. The contents in the box must be properly labeled. An inventory should be recorded prior to shipping media offsite for any reason. The tape librarian is usually responsible for tracking data media in transit. Backup tapes contain the utmost secrets of any organization. All media leaving the primary facility must be kept in secure storage at all times and tracked during transit. New regulations are mandating the use of encryption to protect the standing data on backup tapes. The tape librarian should verify the safe arrival of media at the offsite storage facility. Random media audits at the offsite facility are a good idea. The custodian must track the location and status of all data files outside the primary facility.

Information and media will be disposed of at the end of its life cycle. This is the seventh phase of the SDLC model. A formal authorization process is required to dispose of physical and data assets. Improper controls can lead to the untimely loss of valuable assets. Let's review the common disposal procedures for media:

You're now ready to begin the last major section of this chapter, which covers technical methods of protection.

Data within the database can be protected by using database views. The database view is a read restriction placed on particular columns (attributes) in the database. For example, Figure 7.10 illustrates using a personnel file to create a telephone list. Data that is not to be read for the telephone list has been hidden by using the database view.

Figure 7.10. Database views for security

Another method of limiting access is to use a restricted user interface. The restricted interface may be a menu with particular options grayed out or not displayed at all. Menu access is preferred to prevent the user from having the power of command-line arguments. The command line is difficult to restrict.

A major concern in security is the ability for users to bypass the security label. The security label is a control that specifies who may access the file and how the file may be used. The IS auditor should work with security managers to identify ways in which labels and security settings may be bypassed. Additional compensating controls are necessary to protect against the bypassing of labels and security.

Three types of authentication are possible using discrete information. The most common type of authentication is the user password. The user password is expected to be a secret known only to the user. Unfortunately, many user passwords are poorly constructed or suffer from ineffective protection. When a user logs in with a password, the only information known is that someone has logged in with the password. That is no guarantee of who that person is. Let's take a look at the three types of information, or factors, which can be used to authenticate the user:

Biometrics uses unique physical characteristics to authenticate the identity claimed by the user. This is accomplished by using either physiological characteristics or behavioral characteristics. You are expected to understand the different types of biometric data used for authentication.

Using Behavioral Characteristics

Behavioral characteristics are considered a weak type of authentication because of concerns about their authenticity. Behavior is easier to forge than physical characteristics. For example, in my childhood, I taught my little brother how to speak. As a result, it's nearly impossible to distinguish even the slightest difference in our voices. My father's handwriting impressed me when I was learning to write in cursive. After much practice, my signature in sixth grade looked exactly like his. That illustrates the problem. Let's look at using signatures and voice patterns.

Figure 7.16. Face recognition

Signature dynamics

Signature dynamics is a behavioral form of biometric data. The user's signature is monitored for time duration, pressure, and technique. The advantage is the low cost of implementation. The disadvantage is that many individuals do not write their signature consistently. Some individuals, such as celebrities and authors of this Study Guide, refuse to allow their signature to be digitally recorded because it is still used as the primary means of authenticating legal documents.

Voice pattern

Voice pattern recognition is an inexpensive method of identifying a person by the way they talk. Voice pattern recognition is not the same as speech recognition. Speech recognition assembles sounds into words. Voice pattern analysis checks for characteristics of pitch, tone, and sound duration. A person's voice is analyzed for unique sound characteristics, tone, inflection, and speed. The typical method is to ask a user to repeat a particular pass phrase. The characteristics of the pass phrase are converted into a digital template. Voice pattern recognition is less expensive and less accurate than other types of biometrics. Voice authentication can be fooled by recorded audio playback of a person's voice. Figure 7.17 illustrates voice recognition.

Figure 7.17. Voice pattern analysis in biometrics

Note

As a CISA candidate, you are expected to understand the older biometric techniques of signature dynamics and voice pattern analysis.

Biometrics comprises technology-based systems and hence requires a disciplined approach. Each biometric system follows an SDLC life cycle. As an auditor, you will encounter a growing number of clients using or planning to implement biometric systems. Auditors don't need to be technicians. Our job is to witness whether management did their job of selecting the right system and how it is governed. Let's take a walk through the basic life cycle:

Using biometric systems has some drawbacks. How will the biometric results be used? Is the biometric system expected to provide identification or authentication?

Biometric systems face issues of social acceptability. The users may have concerns about sanitary health issues regarding physical contact or about invasion of privacy. Biometric data must be managed to ensure the security of initial data collection, data distribution, and processing. A biometric data policy is required to specify the data life cycle and control procedures. Biometric data must always be protected for confidentiality and integrity.

Error rates exist in all automated systems, and biometric systems are no different. It is possible for an error to occur during data collection or data processing. The following are various types of errors that can occur in a biometric system:

We have discussed the methods for authenticating a user. Now it is time to discuss the types of access that could be granted on the network.

Figure 7.18. Crossover error rate

The Kerberos single sign-on (SSO) system was developed to improve both security and user satisfaction. The name Kerberos refers to the mythical three-headed dog guarding the gates to the underworld. Kerberos provides security when the end points of the network are safe but the transmission path cannot be trusted—for example, when the servers and workstations are trusted but the network is not.

The concept of operation is for the user to log in once to Kerberos. After login, the Kerberos system authenticates the user and grants access to all resources. The process works as follows:

The belief is that a user with a strong password and strong encryption will improve overall security. Unfortunately, Kerberos works only with specially modified versions of software designed for use with Kerberos. Merely installing Kerberos will not improve security. There are compatibility problems with different versions of implementation.

Special skills and experience are required to make a Kerberos installation successful. First, a knowledgeable installer will understand how to use separate domains to partition Kerberos access for better security. Second, restoring data from tape backup is quite involved. The Kerberos system must be shut down and the date rolled back to the timestamp of the file being restored. As soon as the file is restored, the time clocks must be rolled forward again with the system resynchronized for the users. Any compromise of the Key Distribution Center (KDC) means that the entire system is compromised and must be shut down. Using Kerberos requires highly experienced system administrators. Figure 7.19 illustrates the design of a Kerberos single sign-on.

Figure 7.19. Kerberos single sign-on

Computer networks can be protected from internal and external threats by using firewalls (FWs). The concept is that a specially configured firewall on the network will block unwanted access. However, this is a grossly misunderstood concept, and many organizations do not understand firewall capabilities and limitations. As a result, there can be a false sense of security. Let's consider the advantages and disadvantages of network firewalls:

Network firewalls have undergone several generations of improvement. The first generation was simply a router with a primitive access list specifying the to destination and the sender's from network addresses. Attackers became more sophisticated, and so did the need for better firewalls. The following are the different generations of firewall technology:

The network firewall is the best defense for protecting a network. Each generation provides different levels of cost and protection. Figure 7.20 illustrates the firewalls by generation in relation to the OSI model. We covered the OSI model in Chapter 4, "Networking Technology."

Figure 7.20. Firewall generations compared to the OSI model

Network firewalls can be implemented by using one of three basic designs. The first method is the screened host implementation. The screened host protects a single host through the firewall. The host computer is strongly defended. It is expected that this host may be attacked. Technical manuals may refer to this as the bastion host. Figure 7.21 illustrates the screened host implementation.

The next method of firewall implementation is to install two interface cards in the same host. This method is referred to as to dual-homed. The host computer is configured with the routing disabled. A special software application such as an application proxy relays appropriate communication between the two interface cards. This is the configuration of many Internet firewalls. Figure 7.22 illustrates the dual-homed host.

Figure 7.21. Firewall-screened host

Figure 7.22. Dual-homed host

The third method of firewall implementation is known as the screened subnet, or DMZ design. DMZ is a term that refers to the demilitarized zone between enemy forces on a battlefield. The DMZ design allows for several computers to be placed in a protected subnet that is accessible from the outside and by systems inside the network. Any military veteran will tell you that it's possible to be attacked and killed in the DMZ. The same applies to computers located here. Figure 7.23 illustrates the DMZ concept.

Firewall systems should be implemented to support a separation of duties. Separation of duties is just as important for machines as for personnel. The intention is to provide additional layers of control. Separate firewalls allow tighter access-control rules. Selected data is mirrored from internal production servers to a DMZ server for access by business partners or clients. This eliminates the dangers of direct access to an internal server. In addition, the redundancy improves overall availability. An outage would affect a smaller audience. Figure 7.24 illustrates the separation of duties using a firewall.

Figure 7.23. Screened subnet, also known as DMZ subnet

Figure 7.24. Separation of duties with firewalls

Remote users can often access the network over standard telephone lines with modems. This method completely bypasses security mechanisms provided by the network firewall. The dial-up user may access the network through an access server modem bank or an individual modem on a networked computer. As an IS auditor, you need to determine whether the client has adequate safeguards to prevent this method of circumvention. Are the phone connections to modems properly managed considering the higher level of risk?

Virtual private networks (VPNs) connect remote users over an insecure public network such as the Internet. The connection is virtual because it is temporary with no physical presence. VPN technology is cost-effective and highly flexible. A VPN creates an encrypted tunnel to securely pass data as follows:

There are four types of VPN technology and protocol in use today. ISACA wants you to be familiar with the basic terms for each of the four types of VPN:

SSL and Transport Layer Security (TLS) are commonly used for confidentiality and integrity in the session between the user and the server. Both SSL and TLS operate in a similar manner. The design uses a digital certificate on the server to generate one-way authentication. A secure login to the server can be generated by using Secure Shell (SSH). Encryption occurs along the entire path between the sending and receiving computers. SSH provides end-to-end confidentiality and integrity in a terminal session with the host server.

The IPsec design is the newest development in virtual private networking. IPsec uses ISP gateways with two modes of creating a VPN. Let's start with two important differences in operation of the VPN gateway:

In IPsec virtual private networks, there are two specific operating modes:

Security is managed by the authentication header (AH) and security parameter index (SPI). The authentication header uniquely identifies each packet and provides sequencing information. AH provides authentication, integrity, and nonrepudiation.

The security parameter index provides information about encryption and special handling requirements. This design is based on the older X.25 communication standard you read about in Chapter 4.

Figure 7.25 illustrates the IPsec design.

Figure 7.25. VPN using IPsec transport versus tunnel mode

The goal of every VPN is to grant remote access to authorized users. Data can be shared across the Internet at a very low cost with relative safety if the proper internal controls are implemented. A VPN can be combined with a firewall DMZ by using a separation of duties between internal production servers and the external accessible server. Figure 7.26 illustrates a VPN with a separation of duties between servers.

User demands for wireless access to network resources increase every day. When you read the vendor ads, it appears that wireless can provide security equal to wired access. However, wireless access to networks represents an additional level of threat. Wireless security has been completely compromised by vendors to improve Plug and Play capabilities.

It's relatively simple to construct a wireless LAN. A wireless network can be peer to peer, which is known as ad hoc mode. Another type of wireless LAN is infrastructure mode with the access points (APs) connecting various stations. Several vendors offer low-cost wireless AP that is similar to a wireless hub or router. Each AP is connected to a wired network and broadcasts connectivity to handheld devices.

Figure 7.26. VPN with separation of duties

Usually the range of an AP is 300 feet, equivalent to 100 meters. Users can move freely within the 300-foot broadcast range without losing any connectivity. The individual broadcast area (range) is also known as a cell. This is comparable to the design of cellular telephone networks. Effective range can be increased by combining APs and their multiple cells (service range). WLANs are based on the IEEE 802.11 standard. Let's look at the basic components of a WLAN.

Figure 7.27 shows the basic layout of a wireless network.

Usually the AP is connected to a distribution system such as the existing wired network to provide an infrastructure with greater services for the stations. This is the most common implementation of WLAN.

Figure 7.27. Basic wireless network

The original WLAN standard for wireless network was very slow, operating at only 1Mbps–2Mbps speeds. Three competing WLAN technology standards were established between 1999 and 2003. All three are considered obsolete due to security flaws:

The lack of effective security is an enormous drawback in wireless networking. IEEE's original design of Wired Equivalent Privacy (WEP) proved to be practically worthless. In response, IEEE issued a revised wireless standard.

Technology is a constant series of evolving standards. IEEE helps drive technology by issuing new wireless standards offering better security or longer transmission range. Let's start with improving wireless security.

Emerging demand for wireless connectivity is pushing the boundaries of information security. Moore's law states that computing power will double every 18 months, and at the same time the present methods of security will be reduced in effectiveness by 50 percent.

The challenge of protecting a WLAN can be solved only by a multilevel approach. Every subset of confidentiality, integrity, and availability (CIA) is at risk in WLAN implementations. There is no individual technology that will provide enough protection against the full spectrum of threats. WLAN security requirements can be summarized as follows:

Figure 7.28 provides a simple depiction of the difference between WEP and 802.11i using 802.1X. Notice the changes improving our CIA objectives.

Figure 7.28. Robust security compared to earlier versions

To secure wireless networks and their associated devices requires significant effort, coupled with proper resources and vigilance. It is imperative that management reassess wireless risks at least monthly. The only effective way to maintain security is by constant testing and evaluating systems security controls when wireless technology is being deployed.

Private-key encryption systems use a secret key, which is shared between the authorized sender and the intended receiver. Private-key systems contain two basic components. The first component is the mathematical algorithm for scrambling and unscrambling the message (encrypting and decrypting). The second component is the mathematical key used as a randomizer in the encryption algorithm. The longer the key length, the higher the security it will generate.

A single secret key is carefully shared between the sender and receiver. This is referred to as symmetric-key cryptography (see Figure 7.31). Symmetric-key cryptography is very fast, because the same key is used on both ends. The drawback is that the key must be protected with the highest possible diligence. Anybody who has a copy of the secret key can read the message. Examples of symmetric-key (secret key) cryptography include Data Encryption Standard (DES), which is now obsolete, and the new Advanced Encryption Standard (AES) designed by two Belgian researchers, Joan Daemen and Vincent Rijmen.

Because of the secret-key design of symmetric cryptography, encryption and decryption is very fast and efficient. The drawback is that the secret-key design cannot be used for digital signatures. To do so would expose the key to outsiders. Exchanging the secret key in symmetric cryptography is a major problem.

Asymmetrical cryptography is referred to as public-key cryptography. This design utilizes a separate pair of keys for encryption and decryption. The key pair is composed of a secret key protected by the owner and a second public key that is freely distributed. These two keys are mathematically related to each other. The secret key and public key are generated from a supersized prime number. It is practically impossible for a cryptographic hacker to derive the super prime number or related keys in use.

The strength of public-key cryptography depends on the algorithm used and the encryption key length. To encrypt a message, the sender would use their own secret key and public key, plus the public key of the intended recipient. Figure 7.32 shows the process of encrypting by using public-key (asymmetrical) cryptography.

Figure 7.31. Symmetric-key cryptography

Figure 7.32. Encryption using public-key system

The process of decrypting the message returns it to readable text. To decrypt, the recipient uses their secret key and public key, plus the public key of the sender. The basic concept is that you need only three keys to unlock the data (decryption). If two values were missing, decrypting the file would be impossible. Figure 7.33 shows the process of decrypting by using public-key cryptography.

The design of public-key cryptography eliminates the need to exchange a secret key between the sender and receiver. Public-key cryptography is designed to allow digital signing of files.

Figure 7.33. Decryption using public-key system

The greatest vulnerability in encryption systems is the inherent lack of control. Encryption algorithms are well designed; however, their application or management may be poor. Encryption software and encryption keys should be managed as software applications under the SDLCSDLC. Here are a few tips:

Just imagine what would happen if the organization was backing up data using encryption, and the encryption keys were lost. It could get even worse when you consider the implications to business continuity. Heaven forbid that the backup was required for disclosure under a court order for electronic discovery. Each of these conditions indicates a management failure in which integrity of the organization is lost. Failure to control the use of encryption leads to dramatic consequences.

A digital signature is intended to be an electronic version of a personal signature. The purpose is to indicate that the message was sent by a uniquely identified individual. A digital signature created by running a hash utility against any size of file will generate a 120-bit or 160-bit output. Figure 7.34 illustrates the process of generating a hash file and digital signature.

Figure 7.34. Generating a digital signature

The digital signature is attached to the message file, and both are sent to the recipient. The receiver must use the message file, digital signature file, and the sender's public key to test the validity of the signature. Without testing the digital signature, there is no indication of its authenticity. Figure 7.35 illustrates the process of verifying a digital signature.

Figure 7.35. Verifying a digital signature

There is a new method for sending an encrypted message and the key along with it. This process uses a digital envelope. A message is encrypted along with a session key. The session key is encrypted a second time, using the recipient's public key. After transmission, the recipient can decrypt by using their private key, and then decrypt again by using the sender's public key. The double-step encryption ensures that no one else is able to decrypt the key in transit. Figure 7.36 illustrates the process of using a digital envelope.

Figure 7.36. Using a digital envelope

The newest method for encryption algorithms is the elliptic curve. The concept of an elliptic curve is to generate a three-dimensional space. The encryption key refers to a reference point within those dimensions. It would be extremely difficult to calculate keys generated from an elliptic curve. A small elliptic-curve key is exponentially stronger than one generated by linear math.

Elliptic-curve cryptography is used with wireless encryption. The implementation within wireless encryption is completely compromised; however, the concept of the elliptic-curve algorithm is essentially strong. Unfortunately, a 97-bit elliptic-curve encryption has been cracked from the Web by the same people who cracked the RSA 512-bit encryption key. It took twice as long, but the cracking attack was successful.

Quantum cryptography is based on polarization metrics of random photon light pulses. This promising technology is not available as a commercial product yet. However, the overall design appears to be quite strong.

Consider the process for flying on an airline. The airline issues an electronic ticket to the buyer. The electronic airline ticket is a digital certificate in a human-readable form, while the computer's digital certificate is not readable by humans. Let's walk though the amazing similarity between processing an airline e-ticket and the computer using a PKI digital certificate:

Once again, the only real difference between the airline ticket example and your computer is the terminology—plus, a human can actually read an airline ticket. Now we need to move into email security.

Secure Multipurpose Internet Mail Extensions (S/MIME) was developed so that people could send email across the Internet without having to worry about whether the recipient could read it. The original design was Privacy Enhanced Mail (PEM), developed in 1993. S/MIME was created in 1999 and incorporated several enhancements including support for the newer SHA-1 hash and MD5 hash. Additional support was added for the RSA encryption system and signing time attributes. S/MIME provides authentication of the sender and receiver and also verifies message integrity. S/MIME is the current standard for secure email and attachments. Figure 7.39 illustrates the reason why email security is so important.

Figure 7.39. Email security issues

Encryption-key management is critical to ensure confidentiality and integrity of encrypted data. There are several risks with regard to encryption keys. First, the key itself must be protected from theft or illegal copying. Second is a requirement to use several different keys—one for each purpose. It's important not to overuse a key. This is to ensure integrity of the encrypted files. Each use exposes the key to compromise. Unfortunately, this multitude of keys also creates a significant administrative burden, which if mishandled can turn into a catastrophe.

Encryption keys must be stored with a great deal of care. The keys will need to be managed throughout their life cycle. At a future date, a key will be marked for destruction. Creating, managing, storing, and destroying the keys is of particular concern to the auditor. Few organizations do a good job.