Research in secure routing for Mobile Ad Hoc Networks (MANETs) focuses on designing lightweight, adaptive, and resilient routing protocols that can withstand various network attacks such as blackhole, wormhole, and flooding. Recent studies emphasize integrating cryptographic techniques, trust-based models, and machine learning algorithms to ensure data integrity, authentication, and confidentiality during route discovery and maintenance. Hybrid approaches combining blockchain, artificial intelligence, and swarm intelligence optimization have been proposed to enhance route security and reduce energy consumption. These advanced routing mechanisms improve packet delivery, minimize routing overhead, and maintain robust communication performance even in highly dynamic and adversarial MANET environments.