Here in Sweden GDPR is one of the hottest topics within security. There is a lot of confusion regarding what is needed to be done and what different parties need to do.
First of all, GDPR is a law. Any lawyers out there would probably want to correct me as it´s an EU thing, but in essence it needs to be abided by. Hence, the company lawyer has the last say about what is right or wrong. For me, as an architect, my goal is to deliver possible solutions to the problems that arise when you try to abide by the law.
That said, GDPR, is not the only law to follow. On the contrary, for a public entity there are a number of laws that normally are a lot stricter. GDPR more or less, just enforces those laws more, meaning that the security needs to be ramped up quite a bit to ensure that the risks are managed.
GDPR, from a public entity point of view, should be regarded for all information that is not managed by other laws, and as security and operational requirements for the more sensitive information residing in processes governed by the more stricter laws of secrecy or health data.
As many public entities, especially municipalities, have a rather complex setup of services, including partly outsourcing systems to other municipalities, the amount of information that potentially could fall under GDPR is large meaning that, from a threat perspective, there is a large need of security services.
From my point of view, as a security architect, the first action to take is to conduct a risk analysis, either on a larger scale or more focused on the technology. In the end GDPR demands that a lot of legal issues are managed as well, but as stated before, I only try to sort the problems that have a technical or procedural solution.
Second step is to create a governance structure for managing changes that make sure that GDPR in general and security in specific is adhered to and that mapping to the risk analysis is done. GDPR mandates security by design and privacy by design. This is translated in operational terms to map the risk analysis to the solution so that you could show that the risks are managed in a correct way.
Third step is to manage the standard risks that exist due to the fact that you have an infrastructure to manage, no matter the type of technology used, those are the risks that are classified as You Have if you follow my You3 model. One of the most important steps to do here is to secure your environment against credential theft and lateral movement. You could find an official Microsoft description on Securing Privileged Access here but I strongly advice you to take external help here as it is rather complex to do it yourself.
Fourth step is to secure your databases with encryption. There are many ways of encrypting your databases and if you are running Microsoft SQL Server you´ll find the process rather straight forward with only a small amount of time needed to implement the technology. The processes for key management is a rather different thing however.
Fifth step is to ensure fully working backups of all important data and that all of those are secured as well. Remember to backup your keys as well, otherwise you have built a Do-It-Yourself-wiperware.
Sixth step is to ensure that you monitor your environment and make sure that you catch any attackers sooner rather than later. There are many tools out in the market but make sure that you go for those with built in machine learning and those that utilise information of attacks globally to protect your organisation. Add a good antimalware with ransomware blocking capabilities as well.
There are many more steps to take into account to build a secure environment but the steps taken above will be more than enough to keep you busy for months to come.