The sources provide guidance on protecting businesses from insider threats, offering both preventative and reactive measures. Preventive strategies include conducting security risk assessments, implementing physical security controls, employing strong hiring and training practices, utilizing robust identity and access management, hardening network security, and adhering to general security best practices. Reactive measures focus on identifying potential insider threats through signs such as disgruntled employee behavior, unusual account activity, behavioral changes, suspicious communications, and unexpected lifestyle changes.