There are stricter rules of processing special categories of personal data. These rules are outlined in Article 9 of GDPR.

GDPR restricts how special categories of personal data can be processed. The core principles for data processing as defined by Article 6 still apply, but there are stricter rules of processing special categories of personal data, and additional grounds for processing must be met in order for processing to be lawful.
Article 9.1: There are strict rules for processing special categories of personal data, these categories include:
Article 9.2: At least one of these grounds for processing must be met in order for the above categories of special data to be processed lawfully.
Specific EU or national laws can also be grounds for lawful processing.
There is considerable overlap between the standard six grounds for processing (Article 6) and the grounds for processing special categories of personal data.
If the data subject gives explicit consent for processing and/or if the data subject cannot offer consent but processing is in his/her vital interests, then processing is lawful. Processing is also lawful in most cases of legal obligations and/or with official authority, but neither the performance of a contract nor the organization’s legitimate interests are sufficient grounds for lawful processing of these special categories of data.
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