According to Article 32 of the GDPR, the controller and the processor must implement appropriate technical and organisational measures to ensure a level of security appropriate to the risk of the processing, including the ability to restore the availability and access to personal data in a timely manner in the event of a physical or technical incident1. A personal data breach is defined as a breach of security leading to the accidental or unlawful destruction, loss, alteration, unauthorised disclosure of, or access to, personal data transmitted, stored or otherwise processed2. Therefore, a power outage that results in the loss of availability of customer data for six hours is considered a personal data breach under the GDPR.

Based on the WP 29’s February, 2018 guidance, which was endorsed by the European Data Protection Board, company Z should document the loss of availability to demonstrate accountability3. The guidance states that controllers must document any personal data breaches, comprising the facts relating to the personal data breach, its effects and the remedial action taken, regardless of whether the breach needs to be notified to the supervisory authority or the data subjects. This documentation must enable the supervisory authority to verify compliance with the GDPR and must be made available to the supervisory authority on request4.

The other options (A, C, and D) are not required by the GDPR or the guidance, although they may be advisable or beneficial depending on the circumstances. Option A is not mandatory, as the GDPR only requires the controller to communicate the personal data breach to the data subject when the breach is likely to result in a high risk to the rights and freedoms of natural persons5. A temporary loss of availability may not pose such a high risk, unless it affects the data subject’s essential services or activities. Option C is also not obligatory, as the GDPR only requires the controller to notify the supervisory authority of the personal data breach within 72 hours unless the breach is unlikely to result in a risk to the rights and freedoms of natural persons6. A short-term loss of availability may not entail such a risk, unless it affects a large number of data subjects or sensitive data. Option D is not specified by the GDPR or the guidance, although it may be a good practice to conduct a thorough audit of all security systems after a personal data breach to identify and address any vulnerabilities or weaknesses that may have contributed to the incident or may lead to future incidents. References:

1: Article 32 of the GDPR

2: Article 4 (12) of the GDPR

3: Endorsed WP29 Guidelines

4: Article 33 (5) of the GDPR

5: Article 34 (1) of the GDPR

6: Article 33 (1) of the GDPR

7: Guidelines on Personal data breach notification under Regulation 2016/679, WP250 rev.01

8: Regulation (EU) 2016/679 of the European Parliament and of the Council of 27 April 2016 on the protection of natural persons with regard to the processing of personal data and on the free movement of such data, and repealing Directive 95/46/EC (General Data Protection Regulation)

9: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32016R0679