The retention period for an organization’s social media content should be defined by the records retention policy of the organization, which is a policy that specifies how long and in what format the organization’s records, such as documents, e-mails, or social media posts, should be kept, stored, and disposed of. The records retention policy of the organization should be based on the legal, regulatory, operational, and historical requirements of the organization, and should also consider the risks and benefits of retaining or deleting the records. The records retention policy of the organization should apply to all types of records, regardless of the media or the platform they are created or stored on. The retention policies of each social media service is not a valid way to define the retention period for an organization’s social media content, as they are the policies that specify how long and in what format the social media service keeps, stores, and disposes of the user’s content, not the organization’s content. The retention policies of each social media service may not be aligned with the organization’s legal, regulatory, operational, and historical requirements, and may also not be consistent or reliable. The Chief Information Officer (CIO) is not a valid way to define the retention period for an organization’s social media content, as the CIO is the senior executive who is responsible for the overall strategy, planning, implementation, and management of the organization’s information technology (IT) and information systems (IS), not the records retention policy. The CIO may be involved in the development and approval of the records retention policy, but not in the definition of the retention period for each type of record. The amount of available storage space is not a valid way to define the retention period for an organization’s social media content, as the amount of available storage space is a technical and operational factor that affects the capacity and performance of the organization’s IT and IS, not the records retention policy. The amount of available storage space may not be relevant or sufficient to meet the legal, regulatory, operational, and historical requirements of the organization, and may also change over time. References: Official (ISC)2 Guide to the CISSP CBK, Fifth Edition, Chapter 7: Security Operations, page 365. CISSP All-in-One Exam Guide, Eighth Edition, Chapter 8: Business Continuity and Disaster Recovery Planning, page 500.