The force disclosed the incident on Thursday, stating that it identified the attack on September 14 and caused disruption to some non-emergency systems. Cybersecurity specialists were brought in and "precautionary measures" applied to systems while teams worked to restore services safely.
In a statement, Dyfed-Powys Police said: "At this stage, our investigation has found no evidence that members of the public's personal data has been accessed or compromised as a result of this incident. We are, however, continuing to investigate whether any information relating to our staff may have been accessed or compromised, and are taking all appropriate steps to protect that information, and will provide appropriate advice to colleagues if required."
The force notified the Information Commissioner's Office (ICO), though it did not specify when. The investigation is being managed by Tarian, the regional organised crime unit covering three southern Welsh police force areas, through its regional cybercrime unit.
There is no indication yet of who was behind the attack, how they gained entry, or whether ransomware was involved. Dyfed-Powys Police did not respond to requests for additional details.