If a carrier learns that a cybersecurity event has or may have occurred, the carrier or an outside vendor or service provider designated to act on behalf of the carrier shall conduct a prompt investigation. During the investigation, the carrier or an outside vendor or service provider designated to act on behalf of the carrier, shall, at a minimum: determine as much of the following information as possible: whether a cybersecurity event has occurred; the nature and scope of the cybersecurity event; and identification of nonpublic information that may have been involved in the cybersecurity event; and perform or oversee reasonable measures to restore the security of the information systems compromised in the cybersecurity event to prevent further unauthorized acquisition, release, or use of nonpublic information in the carrier’s possession, custody, or control. If a carrier learns that a cybersecurity event has or may have occurred in a system maintained by a third–party service provider, the carrier shall complete the steps listed in subsection (b) of this section or confirm and document that the third–party service provider has completed those steps. A carrier shall: maintain records concerning all cybersecurity events for a period of at least 5 years from the date of the cybersecurity event; and produce the records on demand of the Commissioner.