NCSC Warns of Hacktivist DoS Attacks on UK Organisations
Summary
The UK's National Cyber Security Centre (NCSC) has issued a warning regarding persistent denial of service (DoS) attacks by Russian-aligned hacktivist groups targeting UK organisations, particularly local government and critical infrastructure operators. The NCSC urges organisations to review their cyber defences and resilience measures.
What changed
The National Cyber Security Centre (NCSC) has issued an alert on January 19, 2026, warning UK organisations, especially local government and critical national infrastructure operators, about ongoing disruptive denial of service (DoS) attacks orchestrated by Russian-aligned hacktivist groups. These attacks, driven by ideology rather than financial gain, aim to cripple services and disable websites, potentially causing significant operational disruption. This alert follows a joint advisory in December 2025 that highlighted similar targeting of entities in NATO and European countries opposing Russia's geopolitical stance.
Organisations are strongly advised to review their cyber defences and enhance their resilience against DoS attacks. The NCSC emphasizes that while DoS attacks may be technically simple, their impact can be substantial, leading to costly downtime and service disruption. The agency encourages all affected organisations to implement the NCSC's freely available guidance to protect against these threats and other cyber risks. Engagement with the NCSC's heightened cyber threat collection is also recommended.
What to do next
- Review cyber defences against DoS attacks
- Enhance cyber resilience and response capabilities
- Implement NCSC guidance for protection against cyber threats
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NCSC issues warning over hacktivist groups disrupting UK organisations and online services
Russian‑aligned hacktivist groups continue to target UK organisations with disruptive cyber attacks
- New alert warns of state-aligned hacktivists targeting UK organisations, looking to cripple services and disable websites.
- Russian groups continue to target organisations in the UK, particularly local government and operators of critical infrastructure.
- Organisations are encouraged to review defences and prepare resilience against attacks. Today, 19th January 2026, the National Cyber Security Centre (NCSC) – a part of GCHQ – has issued an alert highlighting the persistent targeting of UK organisations by Russian state-aligned hacktivist groups aiming to disrupt networks.
Organisations, particularly local government authorities and operators of critical national infrastructure, are being encouraged to review their defences and improve their cyber resilience by preparing and being able to respond to denial of service (DoS) attacks.
Although DoS attacks are typically low in sophistication, a successful attack can disrupt entire systems, costing organisations significant time, money, and operational resilience by having to analyse, defend against, and recover from them.
The alert notes that the ongoing attacks by Russian-aligned hacktivist groups are driven by ideology, over perceived Western support for Ukraine, rather than financial gain, and they operate outside the direct control of the state.
In December 2025, alongside international partners, the NCSC co-sealed an advisory which called out pro-Russian hacktivists groups for targeting government and private sector entities in NATO member states and other European countries that are seen as standing in opposition to Russia’s geopolitical ambitions.
NCSC Director of National Resilience, Jonathon Ellison said:
“We continue to see Russian-aligned hacktivist groups targeting UK organisations and although denial-of-service attacks may be technically simple, their impact can be significant.
“By overwhelming important websites and online systems, these attacks can prevent people from accessing the essential services they depend on every day.
“All organisations, especially those identified in today’s alert, are urged to act now by reviewing and implementing the NCSC’s freely available guidance to protect against DoS attacks and other cyber threats.”
The NCSC has persistently called out malicious cyber activity from Russia and its supporters. In 2023, the NCSC alerted organisations to the emergent risk posed by state-aligned adversaries following the Russian invasion of Ukraine.
Organisations are also encouraged to engage with the NCSC’s heightened cyber threat collection.
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Published
19 January 2026
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