Abstract: A system can detect a change associated with a subscriber identity module (SIM) of a wireless device and generate a data record indicative of the change. In one example, the data record is stored on a digital ledger residing on a cryptographically secured and distributed peer-to-peer network (e.g., blockchain) that stores multiple data records of changes to SIMs of wireless devices. The system can determine whether a wireless device is impacted by malicious activity based on an age of its data record stored on the distributed ledger. For example, an aged data record indicates a lower probability that the wireless device was the subject of a SIM swap fraud whereas a newer data record indicates a higher probability of a SIM swap fraud.