Date format
A convention for representing dates and times. The value 2026-10-14T10:00:00+02:00 includes a date, time and UTC offset. RFC 3339 supports data exchange; a local display format may differ.
Definition and sourcesKNOWLEDGE / FROM A TO Z
Glossary
Technology, explained clearly. Find a term, choose a letter or narrow the topic. Definitions include sources and their review date.
Terms 685 / 685
DDoS (Distributed Denial of Service)
An attack using traffic from multiple sources to exhaust resources and disrupt legitimate access. Defence may require upstream filtering and distributed infrastructure. An application firewall alone cannot handle every kind of DDoS.
Definition and sourcesDebian
A community-developed operating-system distribution. It provides packages and updates; release-branch choice affects stability, available versions and support.
Definition and sourcesDebugging
Systematically finding the cause of a software defect. It includes reproduction, observation and fix verification; random code changes are not a substitute.
Definition and sourcesDeFi
Financial services built on blockchain and smart contracts, such as lending and exchange. They reduce some traditional intermediaries but introduce other dependencies. Risks include contract bugs, liquidity and external data sources.
Definition and sourcesDemand Gen campaigns
A Google Ads campaign type using visual formats to build interest and conversions. Check current documentation for available placements and settings.
Definition and sourcesDeployment
Releasing an application version into an environment. It involves configuration, data compatibility and post-change checks, not merely uploading files.
Definition and sourcesDevOps
An approach bringing software development and operations teams together through collaboration, automation, feedback and continuous delivery. DevOps is not a compulsory tool list or one strictly specified methodology.
Definition and sourcesDevSecOps
Integrating security throughout software development and operations. It combines team responsibility, risk analysis and automated checks. Scanning helps find problems but does not itself establish product security.
Definition and sourcesDigital accessibility
Designing services usable by people with different disabilities. It covers content, keyboard operation, assistive technology and understandability.
Definition and sourcesDirect message
A direct message between platform users. Private describes limited visibility but alone confirms neither end-to-end encryption nor confidentiality from the operator.
Definition and sourcesDirectAdmin
A hosting administration panel for domains, email and accounts. Available functionality depends on permissions and server configuration.
Definition and sourcesDisaster recovery plan
A plan for restoring services after major disruption. It defines roles, dependencies, recovery order and timing goals; it must be exercised, not just documented.
Definition and sourcesDisavow links tool
Google's tool for submitting links a site owner wants discounted. Google advises caution; most websites do not need it.
Definition and sourcesDMARC
A domain policy evaluating SPF or DKIM alignment with the sender domain and requesting handling. The p=none policy monitors rather than requests rejection.
Definition and sourcesDNS (Domain Name System)
A hierarchical, distributed naming system. DNS records can identify IP addresses, mail servers and other information. A domain need not correspond to one website or server; DNS answers are also cached.
Definition and sourcesDNS A record
A DNS record mapping a name to an IPv4 address. It does not redirect URLs or itself configure HTTPS; those belong to other layers.
Definition and sourcesDNS AAAA record
A DNS record mapping a name to an IPv6 address. It should point to a working IPv6 service; incorrect records can harm some users.
Definition and sourcesDNS CAA record
A record specifying which certificate authorities may issue for a domain. Incorrect policy can prevent certificate issuance or renewal.
Definition and sourcesDNS CNAME record
A DNS record identifying an alias's canonical name. It is not an HTTP redirect and generally cannot coexist with other DNS data at that name.
Definition and sourcesDNS MX record
A DNS record naming a domain's receiving mail server and priority. Lower numbers mean higher preference; MX does not configure application email sending.
Definition and sourcesDNS NS record
A record naming an authoritative server for a zone. Registry delegation and zone records need consistency; editing a zone alone may not change delegation.
Definition and sourcesDNS over HTTPS
Sending DNS queries over HTTPS. It protects transport between client and resolver, but the resolver still sees queries; it does not replace DNSSEC.
Definition and sourcesDNS over TLS
Sending DNS over a TLS-encrypted channel, usually on port 853. Transport protection does not hide queries from the chosen resolver.
Definition and sources