Certified Information Systems Security Professional Glossary

Definitions and pro-tips for the CISSP certification.

A

Acceptable Use Policy (AUP)

An Acceptable Use Policy (AUP) defines the rules and guidelines for appropriate use of an organization’s information assets. It details permitted activities, prohibited behaviors, and consequences for violations, covering areas like internet access, data handling, and device usage to mitigate risk and maintain security.

Access Control

Access Control defines and enforces policies governing who or what can access specific resources. It’s a fundamental security principle ensuring confidentiality, integrity, and availability. Implementation spans administrative procedures, physical barriers, and technical mechanisms like authentication and authorization protocols.

Annual Loss Expectancy (ALE)

Annual Loss Expectancy (ALE) is the yearly expected financial loss from a specific risk. It is calculated by multiplying the Single Loss Expectancy (SLE) by the Annual Rate of Occurrence (ARO). This metric helps organizations prioritize security investments based on quantitative risk analysis.

Annual Rate of Occurrence (ARO)

Annual Rate of Occurrence (ARO) is the estimated frequency with which a specific threat is expected to occur within a single year. It is expressed as a number, such as 0.1 for once every ten years or 2 for twice a year.

Asymmetric Encryption

Asymmetric encryption utilizes a key pair – a public key for encryption and a corresponding private key for decryption. This method eliminates the need for secure key exchange, as the public key can be freely distributed. Algorithms include RSA and ECC, though they are computationally intensive and slower than symmetric methods.

Attribute-Based Access Control (ABAC)

Attribute-Based Access Control (ABAC) is a flexible access control model that grants access based on a combination of attributes. These attributes can include user characteristics, resource properties, and environmental conditions like time of day or location. It provides more granular control than RBAC.

B

Bell-LaPadula Model

The Bell-LaPadula Model is a state-machine security model focused on maintaining data confidentiality. It enforces the 'no read up' (Simple Security Property) and 'no write down' (Star Property) rules to prevent sensitive information from leaking to lower security levels.

BIA

A Business Impact Analysis (BIA) identifies critical business functions and the potential consequences of disruptions to those functions. It determines Recovery Time Objectives (RTOs) and Recovery Point Objectives (RPOs) to guide the development of business continuity and disaster recovery plans, minimizing operational and financial losses.

Biba Integrity Model

The Biba Integrity Model is a formal security model designed to ensure data integrity. It utilizes the 'no read down' and 'no write up' rules to prevent low-integrity information from contaminating or corrupting high-integrity data.

Bloom Filter

A Bloom filter is a space-efficient probabilistic data structure used to determine if an element is potentially present in a set. It may return false positives, indicating an element is present when it is not, but will never return false negatives, ensuring absent elements are correctly identified.

Buffer Overflow

A buffer overflow occurs when a program writes data beyond the allocated memory boundary of a buffer. This vulnerability can overwrite adjacent memory locations, causing program crashes, unexpected behavior, or enabling malicious code execution. Exploitation often involves overwriting return addresses on the stack.

Business Continuity Plan (BCP)

A Business Continuity Plan details the strategies and procedures for maintaining essential business functions during and after a disruptive event. It prioritizes operational resilience, focusing on how the organization will continue to operate with reduced resources or altered conditions.

C

Change Management

Change Management is a formal process used to ensure that modifications to the IT environment are recorded, evaluated, and approved before implementation. This prevents unauthorized changes and minimizes the risk of introducing new vulnerabilities or causing system instability.

CIA Triad

The CIA Triad represents core security principles: Confidentiality ensures data access is limited to authorized users. Integrity guarantees data accuracy and completeness. Availability confirms reliable and timely access to information and resources. These principles form the bedrock of information security programs.

Clark-Wilson Model

The Clark-Wilson Model is an integrity model that focuses on commercial environments by using well-formed transactions and separation of duties. It ensures that data is modified only through authorized programs to maintain internal and external consistency.

Common Criteria (ISO/IEC 15408)

Common Criteria (ISO/IEC 15408) is an international standard for evaluating the security claims of IT products. It uses a framework of Protection Profiles and Security Targets to define security requirements, allowing customers to compare products based on standardized evaluation levels.

CompTIA

CompTIA is a leading vendor-neutral certification organization providing globally recognized credentials in IT. Their certifications validate foundational skills and knowledge across various domains, including networking, security, and cloud computing, serving as a common entry point for IT professionals.

Cross-Site Scripting (XSS)

Cross-Site Scripting (XSS) is a web application vulnerability allowing attackers to inject malicious client-side scripts into web pages viewed by other users. This enables attackers to execute arbitrary code in the user's browser, potentially stealing cookies, hijacking sessions, or defacing websites.

Cryptographic Agility

Cryptographic agility refers to a system’s capacity to rapidly and seamlessly transition between different cryptographic algorithms, key lengths, and protocols. This adaptability is crucial for maintaining security in response to evolving threats, algorithm vulnerabilities, and changing regulatory requirements.

Cryptography

Cryptography is the science of secure communication, utilizing mathematical algorithms to protect information confidentiality, integrity, and authenticity. It encompasses encryption, decryption, hashing, and digital signatures. Strong cryptography relies on computational hardness and key management practices.

D

DAC

Discretionary Access Control (DAC) grants resource owners the authority to determine who has access to their data. Permissions are typically managed through access control lists (ACLs) or similar mechanisms, allowing flexible but potentially less secure access management compared to MAC.

Data Classification

Data classification is the process of categorizing information based on its sensitivity, value, and criticality to the organization. This categorization determines the appropriate security controls, handling procedures, and access restrictions applied to protect data from unauthorized disclosure, modification, or destruction.

Data Custodian

A Data Custodian is the individual or entity responsible for the technical implementation of security controls to protect data. They handle backups, integrity checks, and access permissions as directed by the Data Owner to ensure the data remains available and secure.

Data Loss Prevention (DLP)

Data Loss Prevention encompasses technologies and procedures designed to detect and prevent sensitive data from unauthorized disclosure or exfiltration. DLP solutions monitor, inspect, and protect data in use, in motion, and at rest across various endpoints, networks, and cloud environments.

Data Owner

A Data Owner is an executive or manager responsible for the overall classification and protection of a specific data set. They define the access requirements and determine the data's classification level based on its value and sensitivity to the organization.

Data Remanentization

Data remanentization refers to the residual data left on a storage device after standard deletion or formatting. This remaining data can be recovered through forensic techniques. Understanding its persistence is crucial for secure data disposal and preventing unauthorized access to sensitive information.

Data Sanitization

Data Sanitization is the process of permanently removing or destroying data from a storage medium so that it cannot be recovered even with advanced forensic tools. Common methods include clearing, purging, and physical destruction of the media.

Data Sovereignty

Data Sovereignty is the legal concept that digital data is subject to the laws and governance of the country in which it is physically located. This requires organizations to manage data storage carefully to comply with regional privacy regulations.

Defense in Depth

Defense in Depth is a security approach employing multiple, overlapping security controls to protect an organization’s assets. These controls span physical, technical, and administrative domains, creating redundancy and mitigating the impact of any single control failure. It’s a fundamental security principle.

Denial of Service (DoS)

Denial of Service (DoS) attacks exploit vulnerabilities to render a computer or network resource unavailable to legitimate users. These attacks achieve disruption by flooding the target with malicious traffic, exceeding its capacity to respond, or by exploiting system weaknesses to cause crashes or lockups.

DevSecOps

DevSecOps is the integration of security practices into a Continuous Integration/Continuous Deployment (CI/CD) pipeline. It aims to automate security checks throughout the development process, ensuring that security is a shared responsibility between development, security, and operations teams.

Digital Signature

A digital signature provides authentication, integrity, and non-repudiation for electronic messages. It’s created by applying a cryptographic hash function to the message, then encrypting the resulting hash with the sender’s private key. Recipients verify the signature using the sender’s public key.

Disaster Recovery Plan (DRP)

A Disaster Recovery Plan (DRP) outlines the procedures and resources required to restore IT infrastructure and critical data following a disruptive event. It focuses on technical recovery, including data backups, system restoration, and network failover, aiming to minimize downtime and data loss.

Domain Name System Security Extensions (DNSSEC)

Domain Name System Security Extensions (DNSSEC) is a suite of specifications for securing information provided by the DNS. It uses digital signatures and public key cryptography to ensure that the DNS response received by the client is authentic and has not been tampered with.

Due Care

Due Care represents the level of responsibility and caution a prudent individual would exercise under similar circumstances to prevent foreseeable harm. It involves proactively implementing reasonable security controls and safeguards to protect assets and mitigate risks, demonstrating responsible behavior.

Due Diligence

Due Diligence involves conducting thorough investigations and research to gather sufficient information before making decisions or taking actions. It demonstrates a reasonable effort to understand potential risks and liabilities, ensuring informed choices are made regarding security and compliance.

Dynamic Application Security Testing (DAST)

Dynamic Application Security Testing (DAST) is a black-box testing methodology that analyzes an application while it is running. It simulates external attacks to find vulnerabilities such as SQL injection or cross-site scripting in the production or staging environment.

M

MAC (Access Control)

Mandatory Access Control (MAC) is a highly restrictive access control model where the system, not the user, determines access based on pre-defined security labels and clearances. These labels classify both subjects (users) and objects (data), enforcing strict access rules regardless of user preference.

Malware

Malware encompasses malicious software designed to disrupt, damage, or gain unauthorized access to a computer system. This includes viruses, worms, Trojans, ransomware, spyware, and rootkits. Malware can propagate through various vectors, including email attachments, infected websites, and compromised software.

Man-in-the-Middle (MitM) Attack

A Man-in-the-Middle (MitM) attack involves an attacker secretly intercepting and potentially altering communication between two unsuspecting parties. The attacker positions themselves as an intermediary, gaining access to sensitive data exchanged during the session, often without detection by either party.

Mean Time to Repair (MTTR)

Mean Time to Repair (MTTR) is a maintenance metric that measures the average time required to troubleshoot, fix, and return a failed system to full operational status. It is a critical component in calculating overall system availability and reliability.

MTBF

Mean Time Between Failures represents the average time a non-repairable system is predicted to operate before encountering a failure. It’s a key reliability indicator for hardware, calculated by dividing total operational time by the number of failures. Higher MTBF values indicate greater reliability.

Multi-Factor Authentication (MFA)

Multi-Factor Authentication (MFA) enhances security by requiring users to present evidence from two or more independent authentication factors. These factors typically include something the user knows, possesses, or is – significantly reducing the risk of unauthorized access due to compromised credentials.

P

Patch Management

Patch management is a systematic process encompassing identification, acquisition, testing, and deployment of software updates to remediate security vulnerabilities. A comprehensive program minimizes the attack surface by promptly addressing known weaknesses in operating systems, applications, and firmware, reducing exploitation risks.

Penetration Testing

Penetration Testing is an authorized, simulated cyberattack conducted to evaluate the security posture of a system, network, or application. It involves actively exploiting identified vulnerabilities to determine the extent of potential damage and assess the effectiveness of existing security controls.

Physical Access Controls

Physical access controls restrict unauthorized physical access to sensitive areas, equipment, and data. These measures include barriers like fences and locks, surveillance systems, security personnel, and biometric authentication, protecting assets from theft, damage, and unauthorized manipulation.

PKI

Public Key Infrastructure (PKI) is a comprehensive system for managing digital certificates, public and private key pairs, and Certificate Authorities (CAs). It establishes a trusted framework for secure communication and authentication by verifying identities and enabling encrypted data exchange.

Procedure

A Procedure is a detailed, step-by-step set of instructions designed to consistently execute a specific task or process. It outlines the exact sequence of actions required, ensuring uniformity and reducing errors. Procedures are mandatory and often documented within operational manuals or runbooks.

R

Rainbow Table

A Rainbow Table is a precomputed table containing hashes for a large set of passwords, used to accelerate password cracking. It exploits the deterministic nature of hashing algorithms. Modern systems mitigate this threat through salting and the use of computationally expensive key derivation functions.

RBAC

Role-Based Access Control (RBAC) assigns access permissions based on a user’s defined role within an organization. This simplifies access management by granting permissions to roles rather than individual users, improving efficiency and reducing administrative overhead while maintaining security.

Recovery Point Objective (RPO)

Recovery Point Objective (RPO) is the maximum acceptable amount of data loss measured in time, defining the age of files that must be recovered from backup storage for operations to resume. It essentially determines the required frequency of backups.

Recovery Time Objective (RTO)

Recovery Time Objective (RTO) is the maximum tolerable duration of time that a business process or system can be down after a failure or disaster. It defines the target time for restoration to avoid unacceptable consequences associated with a break in business continuity.

Reference Monitor

The Reference Monitor is an abstract machine that mediates all access to objects by subjects based on a defined security policy. To be effective, it must be tamper-proof, always invoked, and small enough to be subjected to rigorous analysis and testing.

Reverse Engineering

Reverse engineering is the analytical process of deconstructing a system, component, or software to reveal its design, architecture, and functionality. This often involves analyzing code, hardware, or protocols to understand how something works, typically without access to original documentation.

Risk Appetite

Risk Appetite is the amount and type of risk that an organization is willing to pursue or retain in order to achieve its strategic business objectives. It serves as a guiding boundary for risk management decisions and the setting of risk tolerance levels.

Risk Management

Risk Management is a systematic process for identifying potential threats and vulnerabilities, assessing their likelihood and impact, and implementing controls to mitigate unacceptable risk. It’s an ongoing cycle of assessment, response, and monitoring to protect organizational assets and achieve objectives.

Risk Transfer

Risk Transfer is a risk treatment strategy that involves shifting the potential financial impact of a risk to a third party. The most common example of risk transfer is the purchase of an insurance policy or outsourcing a specific function to a vendor.

Risk Transference

Risk Transference is a risk response strategy that shifts the financial or operational burden of a risk to a third party. Common examples include purchasing insurance policies or outsourcing specific business functions to a managed service provider. It manages the impact rather than eliminating the risk.

Role-Based Access Control (RBAC)

Role-Based Access Control (RBAC) is an access control mechanism that assigns permissions to specific roles within an organization rather than to individual users. Users are then assigned to these roles, ensuring that access is based on job function.

Root Cause Analysis (RCA)

Root Cause Analysis (RCA) is a systematic process used during the post-incident phase to identify the underlying cause of a security failure. Instead of addressing the immediate symptom, RCA seeks to find why the event happened to prevent future recurrence.

Rootkit

A rootkit is a malicious software suite designed to conceal its existence and maintain persistent, privileged access to a computer system. It operates by modifying core system files, processes, and APIs, making detection extremely difficult and enabling long-term control by an attacker.

RPO

Recovery Point Objective specifies the maximum acceptable data loss measured in time. It determines how frequently data backups must occur to prevent exceeding the defined loss threshold. A shorter RPO implies more frequent backups and potentially higher storage costs, ensuring minimal data loss.

RTO

Recovery Time Objective defines the maximum acceptable length of time an organization can tolerate business process disruption following an incident. It’s a critical metric for business continuity and disaster recovery planning, directly impacting revenue and reputation. RTO drives the selection of recovery strategies.

S

Salt (Cryptography)

Salt is a random string of data added to a password before it is hashed to protect against rainbow table attacks. By ensuring that identical passwords result in different hashes, it forces attackers to crack each password individually.

Secure Boot

Secure Boot is a security standard developed by the UEFI Forum that ensures a device boots using only software that is trusted by the Original Equipment Manufacturer (OEM). It prevents rootkits and bootkits from loading during the system startup process.

Security Assertion Markup Language (SAML)

Security Assertion Markup Language (SAML) is an XML-based open standard for exchanging authentication and authorization data between an Identity Provider (IdP) and a Service Provider (SP). It enables Single Sign-On (SSO) across different security domains.

Security Assessment

A Security Assessment is a systematic evaluation of an organization's information security posture to identify gaps, vulnerabilities, and weaknesses. It involves a combination of vulnerability scanning, penetration testing, and audits to ensure that security controls are operating effectively and as intended.

Security Information and Event Management (SIEM)

Security Information and Event Management (SIEM) is a technology that provides real-time analysis of security alerts generated by applications and network hardware. It combines Security Information Management (SIM) for log collection and Security Event Management (SEM) for real-time monitoring.

Security Kernel

The Security Kernel is the hardware, firmware, and software elements of a trusted computing base that implement the reference monitor concept. It is the most critical part of the system, ensuring that the security policy is enforced across all operations.

Security Orchestration, Automation, and Response (SOAR)

Security Orchestration, Automation, and Response (SOAR) is a stack of compatible software programs that allow an organization to collect data about security threats and respond to low-level security events without human assistance using automated playbooks.

Security Policy

A Security Policy is a high-level document outlining an organization’s commitment to protecting its information assets. It establishes mandatory rules and guidelines for all users and stakeholders, defining acceptable behavior and expectations regarding confidentiality, integrity, and availability. Policies are approved by management.

Separation of Duties

Separation of Duties (SoD) is a fundamental internal control principle that divides critical tasks among multiple individuals. This prevents any single person from having complete control over a sensitive process, mitigating the risk of fraud, errors, and malicious activity through collusion or abuse of privilege.

Service Organization Control 2 (SOC 2)

Service Organization Control 2 (SOC 2) is an auditing procedure that ensures service providers securely manage data to protect the interests of their organization and the privacy of their clients. It is based on Trust Services Criteria: security, availability, processing integrity, confidentiality, and privacy.

Side-Channel Attack

Side-channel attacks exploit implementation details of a cryptographic system to extract secret information. These attacks analyze physical characteristics like power consumption, timing, electromagnetic radiation, or sound to deduce cryptographic keys or internal states, bypassing the algorithm's mathematical strength.

Single Loss Expectancy (SLE)

Single Loss Expectancy (SLE) is the monetary loss expected each time a specific asset is compromised by a threat. It is calculated by multiplying the asset value by the exposure factor. This value provides the foundation for quantitative risk assessment and determining potential financial impacts.

Single Sign-On (SSO)

Single Sign-On (SSO) is an authentication scheme that allows a user to log in with a single set of credentials to access multiple related, yet independent, software systems. It reduces password fatigue and streamlines identity management for the organization.

SOC 2 Report

A SOC 2 (System and Organization Controls) report is an independent auditor's attestation that a service organization's controls are designed and operating effectively. It focuses on five Trust Services Criteria: security, availability, processing integrity, confidentiality, and privacy.

Social Engineering

Social Engineering exploits human psychology to manipulate individuals into performing actions or divulging confidential information. Attackers leverage trust, fear, or helpfulness to bypass security measures, often targeting vulnerabilities in human behavior rather than technical systems.

Software Defined Networking (SDN)

Software Defined Networking (SDN) is a network architecture approach that decouples the control plane from the data plane. This allows network administrators to manage network traffic centrally via software rather than configuring individual hardware devices, increasing agility in large environments.

Software Development Life Cycle (SDLC)

The Software Development Life Cycle (SDLC) is a structured process used by the software industry to design, develop, and test high-quality software. It typically includes phases such as requirements analysis, design, implementation, testing, deployment, and maintenance.

SQL Injection

SQL Injection is a web security vulnerability that enables attackers to interfere with the queries that an application makes to its database. By inserting malicious SQL code into input fields, attackers can bypass security measures, access sensitive data, modify database content, or even execute administrative commands.

SSO

Single Sign-On (SSO) centralizes authentication, enabling users to access multiple applications with one set of credentials. It streamlines user access and improves efficiency by eliminating the need to remember and manage numerous usernames and passwords, enhancing security through centralized policy enforcement.

Standard

A Standard is a specific, mandatory requirement defining precise configurations for hardware, software, or controls. It dictates *how* a policy is implemented, leaving no room for deviation. Compliance is typically verifiable through audits and assessments, ensuring consistent application across an organization.

Static Application Security Testing (SAST)

Static Application Security Testing (SAST) is a white-box testing methodology that analyzes source code, bytecode, or binaries without executing the program. It identifies vulnerabilities like buffer overflows or hardcoded credentials early in the development process, allowing for rapid remediation.

Symmetric Encryption

Symmetric encryption employs a single, secret key for both data encryption and decryption processes. Algorithms like AES and DES offer high speeds, making them efficient for encrypting large volumes of data. However, secure key exchange remains a significant challenge with this method, requiring a trusted channel.

System and Organization Controls (SOC) 2

System and Organization Controls (SOC) 2 is an auditing procedure that ensures service providers securely manage data to protect the interests of their organization and the privacy of their clients. It is based on Trust Services Criteria: security, availability, processing integrity, confidentiality, and privacy.

System Hardening

System hardening is a proactive security process that reduces a system’s attack surface by eliminating unnecessary services, ports, and software. This includes implementing strong configuration settings, applying security patches, and enforcing access controls to minimize vulnerabilities and potential entry points for attackers.