Glossary
Building your knowledge, one term at a time.
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AAA
Authentication, Authorisation and Accounting (AAA) is the trio of services that control and track access to systems and networks. Authentication proves who you are, for example with a password, a certificate or a multi factor…
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Acceptable Use Policy (AUP)
An Acceptable Use Policy (AUP) sets out how people may use an organisation’s IT systems and data. It defines the rules for using devices, accounts, networks, internet access, email and messaging, file shares, cloud services and software.…
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Access Control Entry (ACE)
An Access Control Entry (ACE) is a single rule inside an Access Control List (ACL) that says who can do what to a resource. Each ACE names a security principal such as a user or…
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Access Control List (ACL)
An Access Control List (ACL) is a set of ordered rules that decide who or what is allowed to do something, and who is not. In networking it is a list that filters packets on…
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Active Directory
Active Directory (AD) is Microsoft’s directory service for Windows networks. It stores information about users, computers, groups and policies, and provides a central place to manage sign-in, access to resources, and device configuration. The core component…
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Address Resolution Protocol (ARP)
ARP links IPv4 to Ethernet by mapping an IP address to a MAC address on the local network. When a host needs to send a unicast frame and does not know the target MAC, it…
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Advanced Encryption Standard (AES)
The Advanced Encryption Standard (AES) is a widely used method for encrypting data with the same secret key for locking and unlocking. It works on fixed-size blocks of data and supports key sizes of 128,…
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Advanced Persistent Threat (APT)
An Advanced Persistent Threat (APT) is a deliberate and sustained cyber attack carried out by a highly skilled group, often state sponsored, that gains covert access to a network and maintains that access over a…
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Adware
Adware is a type of malware that presents adverts on a user’s device, often downloaded unknowingly. Once installed it can display pop-up windows, banner ads or full-screen promotions and may track browsing habits or application…
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Algorithm Attack
An algorithm attack targets how something works rather than a simple coding mistake. The attacker feeds inputs that make the system behave in its worst case. That can make it slow down, run out of…
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Allowlist
An allowlist is a list of approved items that are permitted to run, connect or be accessed, with everything else blocked by default. It is used for things like applications and scripts, URLs or domains, IP addresses,…
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ANDing
ANDing is the bitwise operation used to combine two equal-length binary values so that a bit is 1 only when both inputs have a 1 in that position. The truth table is simple: 1 AND…
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APFS
APFS (Apple File System) is Apple’s modern file system for Macs and mobile devices. It became the default with macOS High Sierra and is also used by iOS, iPadOS, watchOS and tvOS. APFS is designed…
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Application Domain
The application domain is the layer where software and services live. It covers the programs users interact with and the back-end logic that powers them. Examples include web apps, mobile apps, desktop apps and background…
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ARP Spoofing
ARP spoofing is the trick of sending forged ARP messages on a local IPv4 network so other devices map an IP address to the attacker’s MAC address. ARP is simple and mostly trust based. Hosts…
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Asset
An asset is anything an organisation relies on to deliver its work and meet its goals. In IT and cyber risk this covers information assets such as customer records and source code, technology assets such as laptops,…
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Attack Surface
An attack surface is the total set of points where an attacker could try to interact with a system and cause harm. It includes internet-facing assets such as websites, APIs, DNS, email services and exposed…
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Attack Vector
An attack vector is the route or method a threat actor uses to reach and affect a target. It is the how of an intrusion: the path taken to gain initial access or to move further once…
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Automated Indicator Sharing (AIS)
Automated Indicator Sharing (AIS) is a system for sending and receiving cyber threat indicators between organisations in near real time so defenders can spot known bad activity faster. In practice it is a feed that…
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Availability
In cyber security, availability is the assurance that authorised users can access the data and services they need without undue delay or interruption. Maintaining availability can be achieved by implementing redundancy, regular backups, resilience planning…