This document summarizes research on detecting blackhole attacks in mobile ad hoc networks (MANETs). It first defines MANETs and describes blackhole attacks, where malicious nodes drop packets to disrupt routing. The document then reviews several approaches for detecting single or cooperative blackhole attacks and compares their assumptions and effectiveness. It finds that while various methods have been proposed, consistently detecting multiple cooperative blackhole nodes remains a challenge, as detection requires cooperation between non-malicious nodes. Future work could involve further simulation-based comparison of detection method performances.