10 Biggest Data Breaches in the UK [2025]

Data breaches pose an escalating threat to UK organizations, with nearly half of businesses (43%) and almost a third of charities (30%) experiencing at least one cyber incident in the past year alone. Phishing attacks remain the leading cause of these breaches, showing ongoing vulnerabilities in human-based security measures. The sheer volume of data compromised remains alarming: with over 30.5 billion records breached across 8,839 publicly disclosed incidents in 2024. Larger enterprises are particularly at risk, with 74% of large businesses and 70% of medium-sized firms reporting breaches or cyberattacks in 2024. The financial implications are severe, averaging $4.53 million per breach, but beyond monetary costs, data breaches break consumer trust and damage organizational reputation, sometimes irreparably. As breaches become more frequent with 21% of organizations experiencing monthly incidents and 18% even weekly the rapid growth of the UK cybersecurity sector, now valued at £11.9 billion annually and employing over 58,000 professionals, highlights the increasing urgency of robust cyber defenses.

In this blog, we analyse the ten most significant data breaches in UK history, uncovering how they occurred, their impacts, and the lessons organizations must learn to safeguard against future threats.

Having one of the largest economies in the world, the UK is an attractive target for cyber criminals because of a few distinct criteria that are given:

The UK is home to numerous global financial institutions, prominent law firms, and major retailers, all of which manage vast amounts of sensitive personal, financial, and corporate data. Financial entities handle detailed customer records and high-value transaction data, while law firms manage confidential case files and sensitive corporate communications. Retailers maintain extensive consumer profiles, including payment and personal details. The highly sensitive nature and high volume of this information make these sectors particularly interesting to cybercriminals looking to commit identity theft, financial fraud, or profit from reselling stolen data on the dark web. Consequently, these organizations consistently remain prime targets for sophisticated cyberattacks.

The UK’s dynamic tech sector and rapid digital transformation have accelerated the adoption of interconnected systems, cloud computing, and digital platforms across businesses of all sizes. While this has enhanced operational efficiency and innovation, it has simultaneously broadened the attack surface available to cybercriminals. The increased reliance on digital connectivity means even a single vulnerable application or unsecured system can provide attackers with an entry point into an entire organization’s infrastructure. As UK businesses continue to embrace digital solutions (from e-commerce platforms and cloud-based services to Internet of Things (IoT) devices) their potential exposure to cyber threats grows, making them especially attractive targets for malicious actors seeking to exploit these digital vulnerabilities.

Unlike many other countries with stringent regulatory frameworks, the UK currently lacks uniform legal obligations requiring all organizations to report every security breach. This fragmented reporting environment frequently results in significant underreporting of cybersecurity incidents. As many breaches remain undisclosed, particularly those perceived as less severe or potentially damaging to an organization’s reputation. The true scale and scope of cyber threats within the UK become difficult to accurately assess. This underreporting not only obscures the full impact of cyber incidents but also slows coordinated efforts to develop effective cybersecurity measures, share threat intelligence, and respond proactively to emerging threats. Consequently, cybercriminals often operate with reduced risk of immediate detection and enforcement.

In the following, you find a list of the largest data breaches in the UK. The data breaches are sorted by the number of impacted accounts in descending order.

3.1 Equifax Data Breach (2017)

Between May and July 2017, Equifax suffered a severe data breach affecting approximately 15 million UK customers, making it the largest data breach reported in the UK to date. The breach occurred due to a vulnerability in Apache Struts, a widely-used open-source web application framework. Cybercriminals exploited the known vulnerability, which Equifax had failed to promptly patch, gaining unauthorized access to sensitive personal data. The compromised information included full names, dates of birth, addresses, telephone numbers, email addresses, driver’s license numbers, partial credit card information, and critical credit reference details. Equifax faced significant criticism for delayed public disclosure of the incident, insufficient incident response measures, and lax security protocols, resulting in reputational damage, regulatory penalties, and several costly legal actions.

Prevention methods:

• Implement regular, rigorous vulnerability assessments and apply critical security patches promptly.

• Maintain advanced monitoring and real-time threat detection capabilities to quickly identify and respond to intrusions.

• Establish robust incident response protocols, including clear and immediate public disclosure processes.

Between July 2017 and April 2018, Dixons Carphone, a leading electronics retailer in the UK, suffered a significant data breach impacting around 10 million customers. Cyber attackers gained unauthorized access to the company’s internal processing systems (reportedly through point-of-sale terminals infected with malware) exposing sensitive personal data including names, addresses, email addresses, and approximately 5.9 million payment card records. Although Dixons Carphone initially underestimated the scale, further investigations revealed the breach’s extensive impact. The UK Information Commissioner’s Office (ICO) later fined Dixons Carphone £500,000, highlighting severe deficiencies in the company’s cybersecurity measures and the delayed response in detecting and mitigating the breach.

Prevention methods:

• Strengthen payment processing systems with end-to-end encryption and tokenization to protect cardholder data.

• Deploy advanced intrusion detection and monitoring solutions to identify and respond rapidly to suspicious activity.

• Ensure timely incident detection and reporting procedures to mitigate breach impact and regulatory penalties.

In January 2020, the UK-based airline EasyJet experienced a significant cyberattack that compromised personal data of approximately 9 million customers. Attackers gained unauthorized access to EasyJet’s booking system (allegedly through a highly sophisticated, targeted attack exploiting vulnerabilities in the airline’s IT infrastructure) obtaining customer names, email addresses, travel booking details, and, notably, payment card information for over 2,200 individuals. EasyJet faced criticism for the delayed public disclosure, waiting four months before informing affected customers, thus exposing them to increased risk of targeted phishing attacks and fraud. The Information Commissioner’s Office (ICO) launched an investigation, ultimately highlighting weaknesses in EasyJet’s cybersecurity practices, especially regarding breach detection and response procedures.

Prevention methods:

• Strengthen access control and authentication protocols, employing multi-factor authentication (e.g., passkeys) to protect customer booking systems.

• Implement real-time monitoring and intrusion detection capabilities to promptly identify and mitigate unauthorized access.

• Ensure rapid and transparent breach notification protocols to reduce the risk of secondary fraud or phishing attacks.

Between July 2011 and July 2012, the UK’s National Health Service (NHS) experienced one of its most serious data breaches when a laptop containing sensitive medical records of approximately 8.6 million individuals went missing from an NHS facility. The laptop, which belonged to an NHS contractor handling medical data analytics, held highly sensitive patient information including names, dates of birth, NHS numbers, and detailed medical histories. Although the laptop was protected by a simple password, it notably lacked encryption, raising significant concerns about potential unauthorized access and misuse of sensitive patient records.

The breach brought intense scrutiny and criticism from regulators, privacy advocates, and the general public, highlighting severe vulnerabilities in how the NHS managed and secured patient data. Investigations revealed systemic failures in the NHS’s approach to data governance, inadequate oversight of third-party contractors, and insufficient awareness among employees regarding data security policies. The Information Commissioner’s Office (ICO) imposed a substantial monetary fine on the NHS, and the incident prompted a nationwide review of data protection procedures within healthcare institutions. Additionally, the breach heightened public anxiety about the safety of personal health information, spurring debates on the urgent need to enhance security measures in healthcare data management.

Prevention methods:

• Mandate full-disk encryption for all portable devices and storage media used within the healthcare sector to protect sensitive patient information.

• Strengthen oversight and security compliance audits for third-party contractors handling NHS data, ensuring adherence to rigorous data protection standards.

• Provide ongoing and comprehensive cybersecurity training to NHS staff and contractors, emphasizing best practices for managing sensitive patient records and preventing data loss or theft.

Between April 2019 and February 2020, Virgin Media experienced a significant data breach due to an unsecured marketing database that was mistakenly left accessible online without password protection. Approximately 900,000 customers’ sensitive personal information, including names, home addresses, email addresses, phone numbers, and details about service contracts, were exposed. Although the breach was discovered internally, Virgin Media faced criticism for allowing the misconfigured database to remain publicly accessible for nearly ten months. The incident highlighted major shortcomings in Virgin Media’s data governance practices, resulting in increased phishing risks and potential misuse of customer data. Affected customers subsequently initiated legal actions against the company, underscoring both financial and reputational consequences.

Prevention methods:

• Implement strict security and access control measures for all databases, especially those containing sensitive customer information.

• Regularly audit infrastructure configurations and employ automated tools to detect and remediate misconfigurations rapidly.

• Provide comprehensive cybersecurity training to employees responsible for managing sensitive data and system configurations.

In June 2015, JD Wetherspoon, one of the UK’s largest and most popular pub chains, suffered a significant cyber incident affecting approximately 656,000 customers. Cyber attackers exploited vulnerabilities in an outdated database associated with the company’s old website and customer Wi-Fi registration service. This breach resulted in the exposure of sensitive personal information including names, email addresses, dates of birth, and phone numbers. More worryingly, approximately 100 customers also had partial payment card details compromised, raising fears about potential financial fraud.

JD Wetherspoon faced intense criticism due to their delay in public disclosure, with customers and regulators only being informed about the breach nearly six months after it occurred, in December 2015. This delay significantly increased the risk of further harm, as affected individuals remained unaware and vulnerable to phishing and fraud attempts. The breach highlighted critical weaknesses in the company’s cybersecurity posture, particularly around legacy system management and data handling practices. It also spurred discussions across the hospitality sector regarding the importance of proactive security measures and transparent communication in the aftermath of data incidents.

Prevention methods:

• Regularly review and securely decommission legacy systems to reduce exposure of outdated databases.

• Strengthen database security by applying robust access controls, encryption, and monitoring measures.

• Establish clear, timely breach reporting procedures to maintain customer trust and comply with regulatory expectations.

Between June and September 2018, British Airways experienced a major data breach impacting approximately 500,000 customers, caused by a sophisticated cyberattack known as “Magecart.” Attackers compromised British Airways’ online payment system by injecting malicious scripts into the company’s website and mobile app. As a result, cybercriminals successfully harvested extensive personal and financial data, including names, email addresses, full payment card details, CVV numbers, and booking information.

British Airways was sharply criticized for inadequate cybersecurity measures and delays in detecting the breach, which lasted nearly three months before discovery. The UK’s Information Commissioner’s Office (ICO) initially intended to fine British Airways a record £183 million for violations of data protection rules under GDPR However, this was later reduced to £20 million after the airline cooperated with the investigation and demonstrated improvements. The incident not only caused significant financial and reputational damage to British Airways but also triggered broader awareness of vulnerabilities in online payment processing within the aviation and travel sectors.

Prevention methods:

• Regularly conduct security testing of website and payment gateways to detect and eliminate vulnerabilities promptly.

• Implement robust web application firewalls (WAFs) and real-time monitoring solutions to identify and block malicious activities immediately.

• Adopt secure coding practices and stringent vendor risk assessments, especially when integrating third-party payment solutions.

In April 2017, the UK-based payday loan provider Wonga suffered a significant cyberattack, resulting in the exposure of sensitive personal and financial information for approximately 245,000 customers. Attackers gained unauthorized access to the company’s systems most likely through weak internal controls and inadequate authentication measures, extracting customer names, email addresses, home addresses, phone numbers, bank account details, and partial payment card information. The breach posed substantial risks to affected customers, leaving them vulnerable to identity theft, phishing scams, and financial fraud.

Wonga promptly informed customers and regulatory authorities upon discovering the breach, but the incident raised serious concerns regarding the company’s cybersecurity defenses and customer data management practices. Investigations revealed inadequacies in Wonga’s security infrastructure, particularly around access control, threat detection, and encryption standards for sensitive financial data. The breach significantly harmed Wonga’s reputation and undermined customer trust, ultimately becoming one of the contributing factors to the company’s financial difficulties and subsequent collapse in 2018.

Prevention methods:

• Implement robust encryption and secure storage practices for financial and personal data to protect against unauthorized access.

• Enhance real-time monitoring and intrusion detection capabilities to swiftly identify breaches and mitigate their impact.

• Conduct regular cybersecurity audits and employee training to maintain compliance with best practices and improve incident response preparedness.

In November 2016, UK telecommunications provider Three Mobile experienced a significant cyberattack, compromising the personal data of approximately 210,000 customers. The breach occurred after cybercriminals gained unauthorized access to the company’s customer account upgrade database using employee login credentials. The attackers were primarily aiming to fraudulently order and intercept expensive mobile handsets, exploiting customers’ personal information (including names, phone numbers, addresses, dates of birth, and account details) to facilitate this scheme.

Three Mobile acted swiftly once the breach was discovered, promptly alerting affected customers and cooperating fully with regulatory authorities. However, the incident raised concerns over the company’s internal security practices, particularly related to employee credential management, access controls, and customer data handling procedures. It highlighted the risks posed by insider threats and phishing attacks targeting employee credentials, emphasizing the necessity of strong internal cybersecurity training and robust authentication mechanisms. The breach caused reputational harm and served as a reminder to the telecom industry about the importance of proactively securing customer data against targeted cyber threats.

Prevention methods:

• Implement multi-factor authentication (e.g., passkeys) for employee access to sensitive customer databases.

• Strengthen internal cybersecurity training to help employees recognize phishing attempts and insider threats.

• Establish continuous monitoring and anomaly detection systems to rapidly identify unauthorized database access or suspicious activities.

In October 2015, UK broadband provider TalkTalk suffered one of the most high-profile data breaches in the nation’s recent history, compromising sensitive personal and financial details of approximately 157,000 customers. The cyberattack was executed via an SQL injection vulnerability, allowing attackers to gain unauthorized access to TalkTalk’s customer database. The compromised data included names, home addresses, email addresses, phone numbers, birth dates, bank account numbers, and sort codes, placing affected customers at serious risk of identity theft and financial fraud.

TalkTalk faced significant criticism for its weak cybersecurity practices, particularly due to inadequate database protections and outdated security measures. Additionally, the company was scrutinized for its initial confusion around the scale and specifics of the breach, contributing to customer anxiety and frustration. The breach severely damaged TalkTalk’s reputation and consumer trust, and the UK Information Commissioner’s Office (ICO) imposed a record fine of £400,000, citing the company’s failure to implement fundamental data security protections. The incident became a major lesson in cybersecurity for UK businesses, highlighting the importance of strong, proactive data protection measures.

Prevention methods:

• Regularly perform security testing, including penetration tests and vulnerability assessments, particularly targeting databases and web applications.

• Employ robust database security measures, such as input validation and query parameterization, to protect against SQL injection attacks.

• Enhance real-time monitoring and response capabilities to swiftly detect and mitigate unauthorized database access.

After looking at the biggest data breaches that happened in UK up to 2025, we notice a few observations that reoccur across these breaches:

A common trend observed across multiple incidents was significant delays in detecting and publicly disclosing the breaches. For instance, the JD Wetherspoon breach occurred in June 2015 but was not publicly disclosed until December 2015, leaving customers unaware of their compromised data for months. Similarly, Equifax faced severe criticism due to a prolonged period between the initial breach in July 2017 and disclosure in September 2017, allowing attackers ample time to exploit sensitive data. Virgin Media’s breach lasted nearly ten months before being detected, significantly amplifying customer vulnerability. These prolonged periods of undisclosed exposure can result in extensive harm, as attackers continue exploiting stolen information without affected customers taking necessary protective measures.

Many breaches in the UK highlighted vulnerabilities stemming from poor management of legacy systems, outdated software, or misconfigured databases. Equifax’s breach involved exploiting an unpatched Apache Struts vulnerability, a known issue that remained unaddressed due to insufficient patch management practices. Virgin Media left a marketing database publicly accessible online without any password or security protections for nearly a year, demonstrating significant gaps in security configuration processes. Similarly, TalkTalk suffered due to a simple SQL injection vulnerability, an exploit easily preventable with proper coding practices and security measures. These cases illustrate how basic cybersecurity hygiene, such as timely updates, secure configuration, vulnerability assessments, and rigorous patch management, is often neglected, leaving systems unnecessarily exposed.

A consistent theme among UK breaches is the attackers’ primary focus on financial data, indicating the high monetary value cybercriminals place on financial information. British Airways and EasyJet breaches specifically involved theft of payment card details, including CVV numbers, putting customers at immediate risk of financial fraud. Similarly, the Dixons Carphone breach resulted in the compromise of nearly 5.9 million payment card records. Wonga’s incident exposed bank account details and partial payment card information, again demonstrating attackers’ clear objective: obtaining sensitive data for financial gain, identity theft, or resale on underground markets. This trend shows the critical importance of implementing stringent protections like encryption, tokenization, and secure transaction systems around all financial data.

Several breaches showcased insufficient internal security controls and inadequate cybersecurity training for employees. For example, the Three Mobile breach occurred after attackers used compromised employee credentials, illustrating vulnerabilities in internal credential management and highlighting the risk of insider threats and credential phishing attacks. The NHS breach, resulting from an unencrypted laptop being lost, further demonstrates weak internal policies concerning data handling, device encryption, and security awareness among staff. These incidents reveal that organizations often underestimate internal security measures, such as robust authentication methods (e.g., multi-factor authentication), regular security awareness training for employees, clear policies for managing sensitive information, and rigorous internal auditing processes to detect and mitigate threats proactively.

Similar to our analysis of the biggest data breaches in the USA the largest data breaches in UK history highlight an unmistakable pattern: most of these cybersecurity incidents could have been prevented. Rather than resulting from highly sophisticated or advanced cyberattacks, many breaches were due to fundamental errors such as outdated systems, poorly secured databases, delayed detection, insufficient employee cybersecurity training, and inadequate internal security controls. These preventable mistakes enabled attackers to exploit basic vulnerabilities and gain extensive access to sensitive data, placing millions of individuals at risk of identity theft, financial fraud, and targeted phishing attacks.

For UK organizations across all sectors and sizes, the takeaway is clear: basic cybersecurity practices and proactive measures must never be overlooked. Protecting sensitive data demands rigorous system maintenance, robust encryption standards, prompt vulnerability patching, secure handling of financial information, and comprehensive internal security protocols. As businesses continue to embrace digital transformation and handle increasingly vast quantities of sensitive customer data, their responsibility to implement and maintain strong cybersecurity standards becomes more crucial than ever.