Gloucester City Council Ransomware Attack 2021: Lessons from the Cl0p Incident
In December 2021, Gloucester City Council became the latest UK local authority to suffer a significant ransomware attack — attributed to the Cl0p ransomware group. The attack disrupted council services for months, affecting the council's revenues and benefits services, planning systems, and customer services. The incident highlighted the persistent vulnerability of UK local authorities to sophisticated ransomware groups.
Gloucester City Council's 2021 ransomware attack disrupted services for months — revenues and benefits, planning, and customer services were all affected.
The Gloucester Attack: What Happened
The Gloucester attack began in December 2021, with the council detecting the intrusion in the days following Christmas. The Cl0p ransomware group is associated with sophisticated, targeted attacks on organisations with known vulnerabilities — typically exploiting unpatched software to gain initial access. The council's systems were significantly disrupted, with key services unable to operate normally for an extended period.
Services Affected
The attack affected multiple council services including revenues and benefits processing, the planning portal, housing register, and customer services. Staff were unable to access key systems, and residents experienced significant service delays. The council communicated through alternative channels while working to restore systems.
Recovery and Remediation
Recovery from the Gloucester attack took several months. The council worked with external incident response specialists and the NCSC to investigate the incident, remove the attackers' access, and restore systems. The experience reinforced the importance of tested recovery capabilities and robust backup systems.
Frequently Asked Questions
How does the Cl0p ransomware group typically attack councils?
The Cl0p group is known for exploiting vulnerabilities in widely-used software — most notoriously the MOVEit file transfer vulnerability in 2023. The group conducts extensive reconnaissance before deploying ransomware, exfiltrating data for double extortion. Defence requires prompt patching of known vulnerabilities, network segmentation to limit lateral movement, and EDR to detect unusual activity.
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