You may only collect personal data for specific, explicitly stated and legitimate purposes. You therefore need to have a clear picture of why you are to process the personal data when you begin to collect it. The purposes set the limits for what you may and may not do, for example what data you may process and for how long you may retain it.
Specific, legitimate purposes
The purposes must be specific and concrete, not vague or imprecise. It is for example not sufficient to state "checks" as the purpose of logging and surveillance without also stating the purpose of the checks. The purpose of the checks might be surveillance for security or technical reasons or to follow up internal rules.
Nor is it normally sufficient for your purpose to be only "to improve users' experience", "IT security", or "future research". These are far too broad and the data subjects cannot judge what such processing of personal data might involve.
The purpose must also be legitimate. This means that the processing of personal data must both have a lawful basis under the General Data Protection Regulation and be carried out in accordance with other applicable legislation and general principles of law.
Inform the data subjects
The data subjects have the right to know why you process their personal data, that is to say what the purposes are. Inform the data subjects when you collect the personal data and also if a data subject requests it.
Document the purposes
Document what the purposes of your personal data processing are. You need this to be able to demonstrate that you are complying with the principle of accountability.
Are you processing already collected personal data in new ways?
If you wish to begin processing personal data that you have already collected in some new way, this must be compatible with the original purposes. You can in such cases cite the same lawful grounds as when you collected the data. Remember to inform the data subjects about the new processing of personal data before it begins.
If you on the other hand wish to use the personal data in a way that is not compatible with the original purposes, this is am entirely new instance of personal data processing. You then need to begin all over again and find a lawful basis for the processing of the personal data, ensure that it is carried out in accordance with the fundamental principles and so on.
Is the new instance of processing of personal data compatible with the original purposes?
When you assess whether a new instance of personal data processing are compatible with earlier purposes, you must among other things take into account and ask yourself the following questions:
- What connections are there between the purpose of the original processing of personal data and the new processing?
- In what context did you collect the personal data? What relationship do the data subjects have to you as data controller? What kind of processing of personal data can the data subjects reasonably expect?
- What kind of personal data are you going to process? Is the data sensitive?
- What consequences can the personal data processing have for the data subjects?
- What security measures do you have, for example authorisation control, encryption and pseudonymisation?
It is as a rule compatible with the original purposes to also process personal data for
- archiving purposes in the public interest
- scientific or historical research purposes
- statistical purposes.
You must however have taken appropriate security measures to protect the data subjects' rights.