CompTIA CSA+ Study Guide. Mike Chapple
Читать онлайн книгу.
server, or performing any other potentially malicious activity.
If the sandboxing solution identifies strange behavior, it blocks the code from entering the organization’s network and flags it for administrator review. This process, also known as code detonation, is an example of an automated reverse engineering technique that takes action based on the observed behavior of software.
In most programming languages, developers write software in a human-readable language such as C/C++, Java, Ruby, or Python. Depending on the programming language, the computer may process this code in one of two ways. In interpreted languages, such as Ruby and Python, the computer works directly from the source code. Reverse engineers seeking to analyze code written in interpreted languages can simply read through the code and often get a good idea of what the code is attempting to accomplish.
In compiled languages, such as Java and C/C++, the developer uses a tool called a compiler to convert the source code into binary code that is readable by the computer. This binary code is what is often distributed to users of the software, and it is very difficult, if not impossible, to examine binary code and determine what it is doing, making the reverse engineering of compiled languages much more difficult. Technologists seeking to reverse engineer compiled code have two options. First, they can attempt to use a specialized program known as a decompiler to convert the binary code back to source code. Unfortunately, however, this process usually does not work very well. Second, they can instrument a specialized environment and carefully monitor how software responds to different inputs in an attempt to discover its inner workings. In either case, reverse engineering compiled software is extremely difficult.
Fingerprinting Software
Although it is difficult to reverse engineer compiled code, technologists can easily detect whether two pieces of compiled code are identical or whether one has been modified. Hashing is a mathematical technique that analyzes a file and computes a unique fingerprint, known as a message digest or hash, for that file. Analysts using hash functions, such as the Secure Hash Algorithm (SHA), can compute the hashes of two files and compare the output values. If the hashes are identical, the file contents are identical. If the hashes differ, the two files contain at least one difference. Hashing software is covered in more detail in Chapter 13, “Cybersecurity Toolkit.”
Reverse engineering hardware is even more difficult than reverse engineering software because the authenticity of hardware often rests in the invisible code embedded within integrated circuits and firmware contents. Although organizations may perform a physical inspection of hardware to detect tampering, it is important to verify that hardware has source authenticity, meaning that it comes from a trusted, reliable source, because it is simply too difficult to exhaustively test hardware.
The U.S. government recognizes the difficulty of ensuring source authenticity and operates a trusted foundry program for critical defense systems. The Department of Defense and National Security Agency (NSA) certify companies as trusted foundries that are approved to create sensitive integrated circuits for government use. Companies seeking trusted foundry status must show that they completely secure the production process, including design, prototyping, packing, assembly, and other elements of the process.
Reverse engineers seeking to determine the function of hardware use some of the same techniques used for compiled software, particularly when it comes to observing behavior. Operating a piece of hardware in a controlled environment and observing how it responds to different inputs provides clues to the functions performed in the hardware. Reverse engineers may also seek to obtain documentation from original equipment manufacturers (OEMs) that provide insight into how components of a piece of hardware function.
Compromising Cisco Routers
According to NSA documents released by Edward Snowden, the U.S. government has engaged in reverse engineering of hardware designed to circumvent security.
Source: “Spiegel supply chain interdiction: Stealthy techniques can crack some of sigints hardest targets” by eff.org licensed under CC By 3.0 US
In a process shown in this photo, NSA employees intercepted packages containing Cisco routers, switches, and other network gear after it left the factory and before it reached the customer. They then opened the packages and inserted covert firmware into the devices that facilitated government monitoring.
Summary
Cybersecurity professionals are responsible for ensuring the confidentiality, integrity, and availability of information and systems maintained by their organizations. Confidentiality ensures that unauthorized individuals are not able to gain access to sensitive information. Integrity ensures that there are no unauthorized modifications to information or systems, either intentionally or unintentionally. Availability ensures that information and systems are ready to meet the needs of legitimate users at the time those users request them. Together, these three goals are known as the CIA Triad.
As cybersecurity analysts seek to protect their organizations, they must evaluate risks to the CIA Triad. This includes identifying vulnerabilities, recognizing corresponding threats, and determining the level of risk that results from vulnerability and threat combinations. Analysts must then evaluate each risk and identify appropriate risk management strategies to mitigate or otherwise address the risk.
Cybersecurity analysts mitigate risks using security controls designed to reduce the likelihood or impact of a risk. Network security controls include network access control (NAC) systems, firewalls, and network segmentation. Secure endpoint controls include hardened system configurations, patch management, Group Policies, and endpoint security software.
Penetration tests and reverse engineering provide analysts with the reassurance that the controls they’ve implemented to mitigate risks are functioning properly. By following a careful risk analysis and control process, analysts significantly enhance the confidentiality, integrity, and availability of information and systems under their control.
Exam Essentials
The three objectives of cybersecurity are confidentiality, integrity, and availability. Confidentiality ensures that unauthorized individuals are not able to gain access to sensitive information. Integrity ensures that there are no unauthorized modifications to information or systems, either intentionally or unintentionally. Availability ensures that information and systems are ready to meet the needs of legitimate users at the time those users request them.
Cybersecurity risks result from the combination of a threat and a vulnerability. A vulnerability is a weakness in a device, system, application, or process that might allow an attack to take place. A threat in the world of cybersecurity is an outside force that may exploit a vulnerability.
Cybersecurity threats may be categorized as adversarial, accidental, structural, or environmental. Adversarial threats are individuals, groups, and organizations that are attempting to deliberately undermine the security of an organization. Accidental threats occur when individuals doing their routine work mistakenly perform an action that undermines security. Structural threats occur when equipment, software, or environmental controls fail due to the exhaustion of resources, exceeding their operational capability or simply failing due to age. Environmental threats occur when natural or man-made disasters occur that are outside the control of the organization.
Networks are made more secure through the use of network access control, firewalls, and segmentation. Network access control (NAC) solutions help security professionals achieve two cybersecurity objectives: limiting network access to authorized individuals and ensuring that systems accessing the organization’s network meet basic security requirements. Network firewalls sit at the boundaries between networks