Distributed denial of service meaning

Distributed denial of service (DDoS) describes a coordinated cyber attack that overwhelms an online service, network or website so legitimate users cannot access it. Attackers flood bandwidth, connections or application resources using many malware‑controlled, compromised devices (a botnet), often via reflection or amplification. The term is descriptive rather than defined in statute. In the UK, such conduct is typically charged as unauthorised acts impairing operation of a computer under the Computer Misuse Act 1990, section 3 (with section 3A covering making or supplying attack tools). In Ireland, equivalent offences arise under the Criminal Justice (Offences Relating to Information Systems) Act 2017. Usage is broadly consistent across England & Wales, Scotland, Northern Ireland and Ireland. Typical legal issues include criminal liability; urgent injunctions and Norwich Pharmacal or other disclosure orders to identify perpetrators; contractual allocation of risk (service levels, indemnities, force majeure); regulatory notifications where availability of personal data is affected (UK GDPR/Irish GDPR) and under the NIS regime for essential/important entities; and cyber insurance coverage. Evidence commonly relies on network logs and third‑party mitigation records.