The main purpose of the Defense Secure Mobile Phones Act of 2025 is to enhance the security of communication for senior officials in the Department of Defense. The law aims to ensure that these officials, as well as employees involved in sensitive national security functions, have access to secure mobile phones that protect against cyber threats. Key provisions of the law require the Secretary of Defense to provide secure mobile phones and telecommunications services to designated officials within 90 days of the law's enactment.