Russian‑aligned hacktivist groups are targeting UK organisations with disruptive cyber-attacks, aiming to cripple essential services and disable websites, the National Cyber Security Centre (NCSC) has warned.

Issuing its latest alert over the malicious activities of Russian-backed hackers, the NCSC said that all organisations, but especially local authorities and critical national infrastructure operators, should tighten their defences in preparation for a wave of denial‑of‑service (DoS) attacks.

According to CISA, hackers have been observed using these “basic” attacks to facilitate attacks against supervisory control and data acquisition (SCADA) networks, ultimately allowing them to compromise devices, change usernames and passwords, and perform reconnaissance. 

“There are probably many points in your service where an attacker can attempt to overload or exhaust available resources, thereby preventing you from serving legitimate users. You should understand where these points are, and in each case, determine whether you, or a supplier, are responsible,” the advisory cautions. 

To minimise the impact of DoS attacks, the NCSC said that organisations should ensure they are ready to deal with resource exhaustion by reviewing the protections their ISP provides, looking into third‑party DDoS mitigation services, and considering the use of a content delivery network for web‑based services. 

Just as important, organisations should ensure that all aspects of their infrastructure can scale rapidly to handle the additional loads of a DoS attack, as well as having a response plan that retains full administrative access and allows for “graceful degradation”.

“By overwhelming important websites and online systems, these attacks can prevent people from accessing the essential services they depend on every day,” said Jonathon Ellison, NCSC director of national resilience.

“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.”

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Last month, the NCSC, along with allies from the US, Europe, and Australia, warned of an uptick in hostile cyber activity, with groups like NoName057(16) attacking government and private sector firms in NATO states and other European countries viewed as hostile to Russian geopolitical interests, including frequent DoS attempts against UK local governments.

Unlike ransomware attacks, the NCSC said that these cyber assaults are not driven by financial gain, but by ideology, and are often linked to Western support for Ukraine. While these hacktivist groups are aligned with Russian government interests, the NCSC said they typically operate outside the direct control of the state.