CISSP Exam Dumps - ISC 2 Credentials Questions and Answers

A Business Continuity Plan (BCP) is considered to be valid when it has been validated by realistic exercises. A BCP is a part of a BCP/DRP that focuses on ensuring the continuous operation of the organization’s critical business functions and processes during and after a disruption or disaster. A BCP should include various components, such as:

• Business impact analysis: a process that identifies and prioritizes the critical business functions and processes, and assesses the potential impacts and risks of a disruption or disaster on them
• Recovery strategies: a process that defines and selects the appropriate methods and resources to recover the critical business functions and processes, such as alternate sites, backup systems, or recovery teams
• BCP document: a document that outlines and details the scope, purpose, and features of the BCP, such as the roles and responsibilities, the recovery procedures, and the contact information
• Testing, training, and exercises: a process that evaluates and validates the effectiveness and readiness of the BCP, and educates and trains the relevant stakeholders, such as the staff, the management, and the customers, on the BCP and their roles and responsibilities
• Maintenance and review: a process that monitors and updates the BCP, and addresses any changes or issues that might affect the BCP, such as the business requirements, the threat landscape, or the feedback and lessons learned

A BCP is considered to be valid when it has been validated by realistic exercises, because it can ensure that the BCP is practical and applicable, and that it can achieve the desired outcomes and objectives in a real-life scenario. Realistic exercises are a type of testing, training, and exercises that involve performing and practicing the BCP with the relevant stakeholders, using simulated or hypothetical scenarios, such as a fire drill, a power outage, or a cyberattack. Realistic exercises can provide several benefits, such as:

• Improving the confidence and competence of the organization and its staff in handling a disruption or disaster
• Enhancing the performance and efficiency of the organization and its systems in recovering from a disruption or disaster
• Increasing the compliance and alignment of the organization and its plans with the internal or external requirements and standards
• Facilitating the monitoring and improvement of the organization and its plans by identifying and addressing any gaps, issues, or risks

The other options are not the criteria for considering a BCP to be valid, but rather the steps or parties that are involved in developing or approving a BCP. When it has been validated by the Business Continuity (BC) manager is not a criterion for considering a BCP to be valid, but rather a step that is involved in developing a BCP. The BC manager is the person who is responsible for overseeing and coordinating the BCP activities and processes, such as the business impact analysis, the recovery strategies, the BCP document, the testing, training, and exercises, and the maintenance and review. The BC manager can validate the BCP by reviewing and verifying the BCP components and outcomes, and ensuring that they meet the BCP standards and objectives. However, the validation by the BC manager is not enough to consider the BCP to be valid, as it does not test or demonstrate the BCP in a realistic scenario. When it has been validated by the board of directors is not a criterion for considering a BCP to be valid, but rather a party that is involved in approving a BCP. The board of directors is the group of people who are elected by the shareholders to represent their interests and to oversee the strategic direction and governance of the organization. The board of directors can approve the BCP by endorsing and supporting the BCP components and outcomes, and allocating the necessary resources and funds for the BCP. However, the approval by the board of directors is not enough to consider the BCP to be valid, as it does not test or demonstrate the BCP in a realistic scenario. When it has been validated by all threat scenarios is not a criterion for considering a BCP to be valid, but rather an unrealistic or impossible expectation for validating a BCP. A threat scenario is a description or a simulation of a possible or potential disruption or disaster that might affect the organization’s critical business functions and processes, such as a natural hazard, a human error, or a technical failure. A threat scenario can be used to test and validate the BCP by measuring and evaluating the BCP’s performance and effectiveness in responding and recovering from the disruption or disaster. However, it is not possible or feasible to validate the BCP by all threat scenarios, as there are too many or unknown threat scenarios that might occur, and some threat scenarios might be too severe or complex to simulate or test. Therefore, the BCP should be validated by the most likely or relevant threat scenarios, and not by all threat scenarios.

Recovery strategies of a Disaster Recovery planning (DRP) must be aligned with the cost/benefit analysis and business objectives. A DRP is a part of a BCP/DRP that focuses on restoring the normal operation of the organization’s IT systems and infrastructure after a disruption or disaster. A DRP should include various components, such as:

• Risk assessment: a process that identifies and evaluates the potential threats and vulnerabilities that might affect the IT systems and infrastructure, and estimates the likelihood and impact of a disruption or disaster
• Recovery objectives: a process that defines and quantifies the acceptable levels of recovery for the IT systems and infrastructure, such as the recovery point objective (RPO), which is the maximum amount of data loss that can be tolerated, and the recovery time objective (RTO), which is the maximum amount of downtime that can be tolerated
• Recovery strategies: a process that selects and implements the appropriate methods and resources to recover the IT systems and infrastructure, such as backup, replication, redundancy, or failover
• DRP document: a document that outlines and details the scope, purpose, and features of the DRP, such as the roles and responsibilities, the recovery procedures, and the contact information
• Testing, training, and exercises: a process that evaluates and validates the effectiveness and readiness of the DRP, and educates and trains the relevant stakeholders, such as the IT staff, the management, and the users, on the DRP and their roles and responsibilities
• Maintenance and review: a process that monitors and updates the DRP, and addresses any changes or issues that might affect the DRP, such as the IT requirements, the threat landscape, or the feedback and lessons learned

Recovery strategies of a DRP must be aligned with the cost/benefit analysis and business objectives, because it can ensure that the DRP is feasible and suitable, and that it can achieve the desired outcomes and objectives in a cost-effective and efficient manner. A cost/benefit analysis is a technique that compares the costs and benefits of different recovery strategies, and determines the optimal one that provides the best value for money. A business objective is a goal or a target that the organization wants to achieve through its IT systems and infrastructure, such as increasing the productivity, profitability, or customer satisfaction. A recovery strategy that is aligned with the cost/benefit analysis and business objectives can help to:

• Optimize the use and allocation of the IT resources and funds for the recovery
• Minimize the negative impacts and risks of a disruption or disaster on the IT systems and infrastructure
• Maximize the positive outcomes and benefits of the recovery for the IT systems and infrastructure
• Support and enable the achievement of the organizational goals and targets through the IT systems and infrastructure

The other options are not the factors that the recovery strategies of a DRP must be aligned with, but rather factors that should be considered or addressed when developing or implementing the recovery strategies of a DRP. Hardware and software compatibility issues are factors that should be considered when developing the recovery strategies of a DRP, because they can affect the functionality and interoperability of the IT systems and infrastructure, and may require additional resources or adjustments to resolve them. Applications’ criticality and downtime tolerance are factors that should be addressed when implementing the recovery strategies of a DRP, because they can determine the priority and urgency of the recovery for different applications, and may require different levels of recovery objectives and resources. Budget constraints and requirements are factors that should be considered when developing the recovery strategies of a DRP, because they can limit the availability and affordability of the IT resources and funds for the recovery, and may require trade-offs or compromises to balance them.

Simulation is the type of business continuity test that includes assessment of resilience to internal and external risks without endangering live operations. Business continuity is the ability of an organization to maintain or resume its critical functions and operations in the event of a disruption or disaster. Business continuity testing is the process of evaluating and validating the effectiveness and readiness of the business continuity plan (BCP) and the disaster recovery plan (DRP) through various methods and scenarios. Business continuity testing can provide several benefits, such as:

• Improving the confidence and competence of the organization and its staff in handling a disruption or disaster
• Enhancing the performance and efficiency of the organization and its systems in recovering from a disruption or disaster
• Increasing the compliance and alignment of the organization and its plans with the internal or external requirements and standards
• Facilitating the monitoring and improvement of the organization and its plans by identifying and addressing any gaps, issues, or risks

There are different types of business continuity tests, depending on the scope, purpose, and complexity of the test. Some of the common types are:

• Walkthrough: a type of business continuity test that involves reviewing and discussing the BCP and DRP with the relevant stakeholders, such as the business continuity team, the management, and the staff. A walkthrough can provide a basic and qualitative assessment of the BCP and DRP, and can help to familiarize and educate the stakeholders with the plans and their roles and responsibilities.
• Simulation: a type of business continuity test that involves performing and practicing the BCP and DRP with the relevant stakeholders, using simulated or hypothetical scenarios, such as a fire drill, a power outage, or a cyberattack. A simulation can provide a realistic and quantitative assessment of the BCP and DRP, and can help to test and train the stakeholders with the plans and their actions and reactions.
• Parallel: a type of business continuity test that involves activating and operating the alternate site or system, while maintaining the normal operations at the primary site or system. A parallel test can provide a comprehensive and comparative assessment of the BCP and DRP, and can help to verify and validate the functionality and compatibility of the alternate site or system.
• Full interruption: a type of business continuity test that involves shutting down and transferring the normal operations from the primary site or system to the alternate site or system. A full interruption test can provide a conclusive and definitive assessment of the BCP and DRP, and can help to evaluate and measure the impact and effectiveness of the plans.

Simulation is the type of business continuity test that includes assessment of resilience to internal and external risks without endangering live operations, because it can simulate various types of risks, such as natural, human, or technical, and assess how the organization and its systems can cope and recover from them, without actually causing any harm or disruption to the live operations. Simulation can also help to identify and mitigate any potential risks that might affect the live operations, and to improve the resilience and preparedness of the organization and its systems.

The other options are not the types of business continuity tests that include assessment of resilience to internal and external risks without endangering live operations, but rather types that have other objectives or effects. Walkthrough is a type of business continuity test that does not include assessment of resilience to internal and external risks, but rather a review and discussion of the BCP and DRP, without any actual testing or practice. Parallel is a type of business continuity test that does not endanger live operations, but rather maintains them, while activating and operating the alternate site or system. Full interruption is a type of business continuity test that does endanger live operations, by shutting them down and transferring them to the alternate site or system.

 Investigating all symptoms to confirm the incident is the first step in the incident response process. An incident is an event that violates or threatens the security, availability, integrity, or confidentiality of the IT systems or data. An incident response is a process that involves detecting, analyzing, containing, eradicating, recovering, and learning from an incident, using various methods and tools. An incident response can provide several benefits, such as:

• Improving the security and risk management of the IT systems and data by identifying and addressing the security weaknesses and gaps
• Enhancing the security and decision making of the IT systems and data by providing the evidence and information for the security analysis, evaluation, and reporting
• Increasing the security and improvement of the IT systems and data by providing the feedback and input for the security response, remediation, and optimization
• Facilitating the compliance and alignment of the IT systems and data with the internal or external requirements and standards

Investigating all symptoms to confirm the incident is the first step in the incident response process, because it can ensure that the incident is verified and validated, and that the incident response is initiated and escalated. A symptom is a sign or an indication that an incident may have occurred or is occurring, such as an alert, a log, or a report. Investigating all symptoms to confirm the incident involves collecting and analyzing the relevant data and information from various sources, such as the IT systems, the network, the users, or the external parties, and determining whether an incident has actually happened or is happening, and how serious or urgent it is. Investigating all symptoms to confirm the incident can also help to:

• Prevent the false positives or negatives that might cause the incident response to be delayed or unnecessary
• Identify the scope and impact of the incident on the IT systems and data
• Notify and inform the appropriate stakeholders and authorities about the incident
• Activate and coordinate the incident response team and resources

The other options are not the first steps in the incident response process, but rather steps that should be done after or along with investigating all symptoms to confirm the incident. Determining the cause of the incident is a step that should be done after investigating all symptoms to confirm the incident, because it can ensure that the root cause and source of the incident are identified and analyzed, and that the incident response is directed and focused. Determining the cause of the incident involves examining and testing the affected IT systems and data, and tracing and tracking the origin and path of the incident, using various techniques and tools, such as forensics, malware analysis, or reverse engineering. Determining the cause of the incident can also help to:

• Understand the nature and behavior of the incident and the attacker
• Detect and resolve any issues or risks caused by the incident
• Prevent and mitigate any future incidents or attacks involving the same or similar cause
• Support and enable the legal or regulatory actions or investigations against the incident or the attacker

Disconnecting the system involved from the network is a step that should be done along with investigating all symptoms to confirm the incident, because it can ensure that the system is isolated and protected from any external or internal influences or interferences, and that the incident response is conducted in a safe and controlled environment. Disconnecting the system involved from the network can also help to:

• Prevent the incident from communicating or connecting with any other system or network, and potentially spreading or escalating the attack
• Prevent the incident from receiving or sending any commands or data, and potentially altering or deleting the evidence
• Prevent the incident from detecting or evading the incident response, and potentially hiding or destroying itself

Isolating and containing the system involved is a step that should be done after investigating all symptoms to confirm the incident, because it can ensure that the incident is confined and restricted, and that the incident response is continued and maintained. Isolating and containing the system involved involves applying and enforcing the appropriate security measures and controls to limit or stop the activity and impact of the incident on the IT systems and data, such as firewall rules, access policies, or encryption keys. Isolating and containing the system involved can also help to:

• Minimize the damage and loss caused by the incident on the IT systems and data
• Maximize the recovery and restoration of the IT systems and data
• Support and enable the eradication and removal of the incident from the IT systems and data
• Facilitate the learning and improvement of the IT systems and data from the incident

 Making a copy of the hard drive should be the first action to protect the chain of evidence when a desktop computer is involved. A chain of evidence, also known as a chain of custody, is a process that documents and preserves the integrity and authenticity of the evidence collected from a crime scene, such as a desktop computer. A chain of evidence should include information such as:

• The identity and role of the person who collected, handled, or transferred the evidence
• The date and time of the collection, handling, or transfer of the evidence
• The location and condition of the evidence
• The method and tool used to collect, handle, or transfer the evidence
• The signature or seal of the person who collected, handled, or transferred the evidence

Making a copy of the hard drive should be the first action to protect the chain of evidence when a desktop computer is involved, because it can ensure that the original hard drive is not altered, damaged, or destroyed during the forensic analysis, and that the copy can be used as a reliable and admissible source of evidence. Making a copy of the hard drive should also involve using a write blocker, which is a device or a software that prevents any modification or deletion of the data on the hard drive, and generating a hash value, which is a unique and fixed identifier that can verify the integrity and consistency of the data on the hard drive.

The other options are not the first actions to protect the chain of evidence when a desktop computer is involved, but rather actions that should be done after or along with making a copy of the hard drive. Taking the computer to a forensic lab is an action that should be done after making a copy of the hard drive, because it can ensure that the computer is transported and stored in a secure and controlled environment, and that the forensic analysis is conducted by qualified and authorized personnel. Starting documenting is an action that should be done along with making a copy of the hard drive, because it can ensure that the chain of evidence is maintained and recorded throughout the forensic process, and that the evidence can be traced and verified. Turning off the computer is an action that should be done after making a copy of the hard drive, because it can ensure that the computer is powered down and disconnected from any network or device, and that the computer is protected from any further damage or tampering.

WEP uses a small range Initialization Vector (IV) is the factor that contributes to the weakness of Wired Equivalent Privacy (WEP) protocol. WEP is a security protocol that provides encryption and authentication for wireless networks, such as Wi-Fi. WEP uses the RC4 stream cipher to encrypt the data packets, and the CRC-32 checksum to verify the data integrity. WEP also uses a shared secret key, which is concatenated with a 24-bit Initialization Vector (IV), to generate the keystream for the RC4 encryption. WEP has several weaknesses and vulnerabilities, such as:

• WEP uses a small range Initialization Vector (IV), which results in 16,777,216 (2^24) possible values. This might seem large, but it is not enough for a high-volume wireless network, where the same IV can be reused frequently, creating keystream reuse and collisions. An attacker can capture and analyze the encrypted data packets that use the same IV, and recover the keystream and the secret key, using techniques such as the Fluhrer, Mantin, and Shamir (FMS) attack, or the KoreK attack.
• WEP uses a weak integrity check, which is the CRC-32 checksum. The CRC-32 checksum is a linear function that can be easily computed and manipulated by anyone who knows the keystream. An attacker can modify the encrypted data packets and the checksum, without being detected, using techniques such as the bit-flipping attack, or the chop-chop attack.
• WEP uses a static and shared secret key, which is manually configured and distributed among all the wireless devices that use the same network. The secret key is not changed or refreshed automatically, unless the administrator does it manually. This means that the secret key can be exposed or compromised over time, and that all the wireless devices can be affected by a single key breach. An attacker can also exploit the weak authentication mechanism of WEP, which is based on the secret key, and gain unauthorized access to the network, using techniques such as the authentication spoofing attack, or the shared key authentication attack.

WEP has been deprecated and replaced by more secure protocols, such as Wi-Fi Protected Access (WPA) or Wi-Fi Protected Access II (WPA2), which use stronger encryption and authentication methods, such as the Temporal Key Integrity Protocol (TKIP), the Advanced Encryption Standard (AES), or the Extensible Authentication Protocol (EAP).

The other options are not factors that contribute to the weakness of WEP, but rather factors that are irrelevant or incorrect. WEP does not use Message Digest 5 (MD5), which is a hash function that produces a 128-bit output from a variable-length input. WEP does not use Diffie-Hellman, which is a method for generating a shared secret key between two parties. WEP does use an Initialization Vector (IV), which is a 24-bit value that is concatenated with the secret key.

 Implementing logical network segmentation at the switches is the most effective layer of security the organization could have implemented to mitigate the attacker’s ability to gain further information. Logical network segmentation is the process of dividing a network into smaller subnetworks or segments based on criteria such as function, location, or security level. Logical network segmentation can be implemented at the switches, which are devices that operate at the data link layer of the OSI model and forward data packets based on the MAC addresses. Logical network segmentation can provide several benefits, such as:

• Isolating network traffic and reducing congestion and collisions
• Enhancing performance and efficiency of the network
• Improving security and confidentiality of the network
• Restricting the scope and impact of attacks
• Enforcing access control and security policies
• Facilitating monitoring and auditing of the network

Logical network segmentation can mitigate the attacker’s ability to gain further information by limiting the visibility and access of the sniffer to the segment where it is installed. A sniffer is a tool that captures and analyzes the data packets that are transmitted over a network. A sniffer can be used for legitimate purposes, such as troubleshooting, testing, or monitoring the network, or for malicious purposes, such as eavesdropping, stealing, or modifying the data. A sniffer can only capture the data packets that are within its broadcast domain, which is the set of devices that can communicate with each other without a router. By implementing logical network segmentation at the switches, the organization can create multiple broadcast domains and isolate the sensitive or critical data from the compromised segment. This way, the attacker can only see the data packets that belong to the same segment as the sniffer, and not the data packets that belong to other segments. This can prevent the attacker from gaining further information or accessing other resources on the network.

The other options are not the most effective layers of security the organization could have implemented to mitigate the attacker’s ability to gain further information, but rather layers that have other limitations or drawbacks. Implementing packet filtering on the network firewalls is not the most effective layer of security, because packet filtering only examines the network layer header of the data packets, such as the source and destination IP addresses, and does not inspect the payload or the content of the data. Packet filtering can also be bypassed by using techniques such as IP spoofing or fragmentation. Installing Host Based Intrusion Detection Systems (HIDS) is not the most effective layer of security, because HIDS only monitors and detects the activities and events on a single host, and does not prevent or respond to the attacks. HIDS can also be disabled or evaded by the attacker if the host is compromised. Requiring strong authentication for administrators is not the most effective layer of security, because authentication only verifies the identity of the users or processes, and does not protect the data in transit or at rest. Authentication can also be defeated by using techniques such as phishing, keylogging, or credential theft.

Network Behavior Analysis (NBA) tools are the best network defense against unknown types of attacks or stealth attacks in progress. NBA tools are devices or software that monitor and analyze the network traffic and activities, and detect any anomalies or deviations from the normal or expected behavior. NBA tools use various techniques, such as statistical analysis, machine learning, artificial intelligence, or heuristics, to establish a baseline of the network behavior, and to identify any outliers or indicators of compromise. NBA tools can provide several benefits, such as:

• Detecting unknown types of attacks or stealth attacks that are not signature-based or rule-based, and that can evade or bypass other network defenses, such as firewalls, IDS, or IPS.
• Detecting advanced persistent threats (APTs) that are low and slow, and that can remain undetected for a long time, by correlating and aggregating the network events and data over time and across different sources.
• Detecting insider threats or compromised hosts that are authorized and trusted, but that exhibit malicious or suspicious behavior, by profiling and classifying the network entities and their interactions.
• Providing early warning and alerting of the potential or ongoing attacks, and facilitating the investigation and response of the incidents, by providing rich and contextual information about the network behavior and the attack vectors.

The other options are not the best network defense against unknown types of attacks or stealth attacks in progress, but rather network defenses that have other limitations or drawbacks. Intrusion Prevention Systems (IPS) are devices or software that monitor and block the network traffic and activities that match the predefined signatures or rules of known attacks. IPS can provide a proactive and preventive layer of security, but they cannot detect or stop unknown types of attacks or stealth attacks that do not match any signatures or rules, or that can evade or disable the IPS. Intrusion Detection Systems (IDS) are devices or software that monitor and alert the network traffic and activities that match the predefined signatures or rules of known attacks. IDS can provide a reactive and detective layer of security, but they cannot detect or alert unknown types of attacks or stealth attacks that do not match any signatures or rules, or that can evade or disable the IDS. Stateful firewalls are devices or software that filter and control the network traffic and activities based on the state and context of the network sessions, such as the source and destination IP addresses, port numbers, protocol types, and sequence numbers. Stateful firewalls can provide a granular and dynamic layer of security, but they cannot filter or control unknown types of attacks or stealth attacks that use valid or spoofed network sessions, or that can exploit or bypass the firewall rules.

 The purpose of an Internet Protocol (IP) spoofing attack is to convince a system that it is communicating with a known entity. IP spoofing is a technique that involves creating and sending IP packets with a forged source IP address, which is usually the IP address of a trusted or authorized host. IP spoofing can be used for various malicious purposes, such as:

• Bypassing IP-based access control lists (ACLs) or firewalls that filter traffic based on the source IP address.
• Launching denial-of-service (DoS) or distributed denial-of-service (DDoS) attacks by flooding a target system with spoofed packets, or by reflecting or amplifying the traffic from intermediate systems.
• Hijacking or intercepting a TCP session by predicting or guessing the sequence numbers and sending spoofed packets to the legitimate parties.
• Gaining unauthorized access to a system or network by impersonating a trusted or authorized host and exploiting its privileges or credentials.

The purpose of IP spoofing is to convince a system that it is communicating with a known entity, because it allows the attacker to evade detection, avoid responsibility, and exploit trust relationships.

The other options are not the main purposes of IP spoofing, but rather the possible consequences or methods of IP spoofing. To send excessive amounts of data to a process, making it unpredictable is a possible consequence of IP spoofing, as it can cause a DoS or DDoS attack. To intercept network traffic without authorization is a possible method of IP spoofing, as it can be used to hijack or intercept a TCP session. To disguise the destination address from a target’s IP filtering devices is not a valid option, as IP spoofing involves forging the source address, not the destination address.

Data at rest on a Storage Area Network (SAN) is located at the physical layer of the Open System Interconnection (OSI) model. The OSI model is a conceptual framework that describes how data is transmitted and processed across different layers of a network. The OSI model consists of seven layers: application, presentation, session, transport, network, data link, and physical. The physical layer is the lowest layer of the OSI model, and it is responsible for the transmission and reception of raw bits over a physical medium, such as cables, wires, or optical fibers. The physical layer defines the physical characteristics of the medium, such as voltage, frequency, modulation, connectors, etc. The physical layer also deals with the physical topology of the network, such as bus, ring, star, mesh, etc.

A Storage Area Network (SAN) is a dedicated network that provides access to consolidated and block-level data storage. A SAN consists of storage devices, such as disks, tapes, or arrays, that are connected to servers or clients via a network infrastructure, such as switches, routers, or hubs. A SAN allows multiple servers or clients to share the same storage devices, and it provides high performance, availability, scalability, and security for data storage. Data at rest on a SAN is located at the physical layer of the OSI model, because it is stored as raw bits on the physical medium of the storage devices, and it is accessed by the servers or clients through the physical medium of the network infrastructure.

Link Control Protocol (LCP) is used by the Point-to-Point Protocol (PPP) to determine packet formats. PPP is a data link layer protocol that provides a standard method for transporting network layer packets over point-to-point links, such as serial lines, modems, or dial-up connections. PPP supports various network layer protocols, such as IP, IPX, or AppleTalk, and it can encapsulate them in a common frame format. PPP also provides features such as authentication, compression, error detection, and multilink aggregation. LCP is a subprotocol of PPP that is responsible for establishing, configuring, maintaining, and terminating the point-to-point connection. LCP negotiates and agrees on various options and parameters for the PPP link, such as the maximum transmission unit (MTU), the authentication method, the compression method, the error detection method, and the packet format. LCP uses a series of messages, such as configure-request, configure-ack, configure-nak, configure-reject, terminate-request, terminate-ack, code-reject, protocol-reject, echo-request, echo-reply, and discard-request, to communicate and exchange information between the PPP peers.

The other options are not used by PPP to determine packet formats, but rather for other purposes. Layer 2 Tunneling Protocol (L2TP) is a tunneling protocol that allows the creation of virtual private networks (VPNs) over public networks, such as the Internet. L2TP encapsulates PPP frames in IP datagrams and sends them across the tunnel between two L2TP endpoints. L2TP does not determine the packet format of PPP, but rather uses it as a payload. Challenge Handshake Authentication Protocol (CHAP) is an authentication protocol that is used by PPP to verify the identity of the remote peer before allowing access to the network. CHAP uses a challenge-response mechanism that involves a random number (nonce) and a hash function to prevent replay attacks. CHAP does not determine the packet format of PPP, but rather uses it as a transport. Packet Transfer Protocol (PTP) is not a valid option, as there is no such protocol with this name. There is a Point-to-Point Protocol over Ethernet (PPPoE), which is a protocol that encapsulates PPP frames in Ethernet frames and allows the use of PPP over Ethernet networks. PPPoE does not determine the packet format of PPP, but rather uses it as a payload.

The transport layer of the Transmission Control Protocol/Internet Protocol (TCP/IP) stack is responsible for negotiating and establishing a connection with another node. The TCP/IP stack is a simplified version of the OSI model, and it consists of four layers: application, transport, internet, and link. The transport layer is the third layer of the TCP/IP stack, and it is responsible for providing reliable and efficient end-to-end data transfer between two nodes on a network. The transport layer uses protocols, such as Transmission Control Protocol (TCP) or User Datagram Protocol (UDP), to segment, sequence, acknowledge, and reassemble the data packets, and to handle error detection and correction, flow control, and congestion control. The transport layer also provides connection-oriented or connectionless services, depending on the protocol used.

TCP is a connection-oriented protocol, which means that it establishes a logical connection between two nodes before exchanging data, and it maintains the connection until the data transfer is complete. TCP uses a three-way handshake to negotiate and establish a connection with another node. The three-way handshake works as follows:

• The client sends a SYN (synchronize) packet to the server, indicating its initial sequence number and requesting a connection.
• The server responds with a SYN-ACK (synchronize-acknowledge) packet, indicating its initial sequence number and acknowledging the client’s request.
• The client responds with an ACK (acknowledge) packet, acknowledging the server’s response and completing the connection.

UDP is a connectionless protocol, which means that it does not establish or maintain a connection between two nodes, but rather sends data packets independently and without any guarantee of delivery, order, or integrity. UDP does not use a handshake or any other mechanism to negotiate and establish a connection with another node, but rather relies on the application layer to handle any connection-related issues.

 Packet filtering operates at the network layer of the Open System Interconnection (OSI) model. The OSI model is a conceptual framework that describes how data is transmitted and processed across different layers of a network. The OSI model consists of seven layers: application, presentation, session, transport, network, data link, and physical. The network layer is the third layer from the bottom of the OSI model, and it is responsible for routing and forwarding data packets between different networks or subnets. The network layer uses logical addresses, such as IP addresses, to identify the source and destination of the data packets, and it uses protocols, such as IP, ICMP, or ARP, to perform the routing and forwarding functions.

Packet filtering is a technique that controls the access to a network or a host by inspecting the incoming and outgoing data packets and applying a set of rules or policies to allow or deny them. Packet filtering can be performed by devices, such as routers, firewalls, or proxies, that operate at the network layer of the OSI model. Packet filtering typically examines the network layer header of the data packets, such as the source and destination IP addresses, the protocol type, or the fragmentation flags, and compares them with the predefined rules or policies. Packet filtering can also examine the transport layer header of the data packets, such as the source and destination port numbers, the TCP flags, or the sequence numbers, and compare them with the rules or policies. Packet filtering can provide a basic level of security and performance for a network or a host, but it also has some limitations, such as the inability to inspect the payload or the content of the data packets, the vulnerability to spoofing or fragmentation attacks, or the complexity and maintenance of the rules or policies.

The other options are not techniques that operate at the network layer of the OSI model, but rather at other layers. Port services filtering is a technique that controls the access to a network or a host by inspecting the transport layer header of the data packets and applying a set of rules or policies to allow or deny them based on the port numbers or the services. Port services filtering operates at the transport layer of the OSI model, which is the fourth layer from the bottom. Content filtering is a technique that controls the access to a network or a host by inspecting the application layer payload or the content of the data packets and applying a set of rules or policies to allow or deny them based on the keywords, URLs, file types, or other criteria. Content filtering operates at the application layer of the OSI model, which is the seventh and the topmost layer. Application access control is a technique that controls the access to a network or a host by inspecting the application layer identity or the credentials of the users or the processes and applying a set of rules or policies to allow or deny them based on the roles, permissions, or other attributes. Application access control operates at the application layer of the OSI model, which is the seventh and the topmost layer.

Adding a new rule to the application layer firewall is the most suited to quickly implement a control for an input validation and exception handling vulnerability on a critical web-based system. An input validation and exception handling vulnerability is a type of vulnerability that occurs when a web-based system does not properly check, filter, or sanitize the input data that is received from the users or other sources, or does not properly handle the errors or exceptions that are generated by the system. An input validation and exception handling vulnerability can lead to various attacks, such as:

• Injection attacks, such as SQL injection, command injection, or cross-site scripting (XSS), where the attacker inserts malicious code or commands into the input data that are executed by the system or the browser, resulting in data theft, data manipulation, or remote code execution.
• Buffer overflow attacks, where the attacker sends more input data than the system can handle, causing the system to overwrite the adjacent memory locations, resulting in data corruption, system crash, or arbitrary code execution.
• Denial-of-service (DoS) attacks, where the attacker sends malformed or invalid input data that cause the system to generate excessive errors or exceptions, resulting in system overload, resource exhaustion, or system failure.

An application layer firewall is a device or software that operates at the application layer of the OSI model and inspects the application layer payload or the content of the data packets. An application layer firewall can provide various functions, such as:

• Filtering the data packets based on the application layer protocols, such as HTTP, FTP, or SMTP, and the application layer attributes, such as URLs, cookies, or headers.
• Blocking or allowing the data packets based on the predefined rules or policies that specify the criteria for the application layer protocols and attributes.
• Logging and auditing the data packets for the application layer protocols and attributes.
• Modifying or transforming the data packets for the application layer protocols and attributes.

Adding a new rule to the application layer firewall is the most suited to quickly implement a control for an input validation and exception handling vulnerability on a critical web-based system, because it can prevent or reduce the impact of the attacks by filtering or blocking the malicious or invalid input data that exploit the vulnerability. For example, a new rule can be added to the application layer firewall to:

• Reject or drop the data packets that contain SQL statements, shell commands, or script tags in the input data, which can prevent or reduce the injection attacks.
• Reject or drop the data packets that exceed a certain size or length in the input data, which can prevent or reduce the buffer overflow attacks.
• Reject or drop the data packets that contain malformed or invalid syntax or characters in the input data, which can prevent or reduce the DoS attacks.

Adding a new rule to the application layer firewall can be done quickly and easily, without requiring any changes or patches to the web-based system, which can be time-consuming and risky, especially for a critical system. Adding a new rule to the application layer firewall can also be done remotely and centrally, without requiring any physical access or installation on the web-based system, which can be inconvenient and costly, especially for a distributed system.

The other options are not the most suited to quickly implement a control for an input validation and exception handling vulnerability on a critical web-based system, but rather options that have other limitations or drawbacks. Blocking access to the service is not the most suited option, because it can cause disruption and unavailability of the service, which can affect the business operations and customer satisfaction, especially for a critical system. Blocking access to the service can also be a temporary and incomplete solution, as it does not address the root cause of the vulnerability or prevent the attacks from occurring again. Installing an Intrusion Detection System (IDS) is not the most suited option, because IDS only monitors and detects the attacks, and does not prevent or respond to them. IDS can also generate false positives or false negatives, which can affect the accuracy and reliability of the detection. IDS can also be overwhelmed or evaded by the attacks, which can affect the effectiveness and efficiency of the detection. Patching the application source code is not the most suited option, because it can take a long time and require a lot of resources and testing to identify, fix, and deploy the patch, especially for a complex and critical system. Patching the application source code can also introduce new errors or vulnerabilities, which can affect the functionality and security of the system. Patching the application source code can also be difficult or impossible, if the system is proprietary or legacy, which can affect the feasibility and compatibility of the patch.

Identity as a Service (IDaaS) is the best contract in offloading the task of account management from the IT staff. IDaaS is a cloud-based service that provides identity and access management (IAM) functions, such as user authentication, authorization, provisioning, deprovisioning, password management, single sign-on (SSO), and multifactor authentication (MFA). IDaaS can help the organization to streamline and automate the account management process, reduce the workload and costs of the IT staff, and improve the security and compliance of the user accounts. IDaaS can also support the contractors who have limited onsite time, as they can access the organization’s resources remotely and securely through the IDaaS provider.

The other options are not as effective as IDaaS in offloading the task of account management from the IT staff, as they do not provide IAM functions. Platform as a Service (PaaS) is a cloud-based service that provides a platform for developing, testing, and deploying applications, but it does not manage the user accounts for the applications. Desktop as a Service (DaaS) is a cloud-based service that provides virtual desktops for users to access applications and data, but it does not manage the user accounts for the virtual desktops. Software as a Service (SaaS) is a cloud-based service that provides software applications for users to use, but it does not manage the user accounts for the software applications.