The papers in this proceedings were presented at the Third ACM International Workshop on Reliability, Availability, and Security (WRAS 2010), held July 29th, 2010 in conjunction with PODC 2010 Zurich, Switzerland. The WRAS workshop is dedicated to both theoretical and practical aspects of reliability, availability, and security, with an emphasis on parallel and distributed systems. The first edition of the workshop was held in Paris, France in 2007 in conjunction with SSS, the international Symposium on Stabilization, Safety, and Security. The second edition of the workshop was held in Hiroshima, Japan in conjunction with PDCAT 2009, the tenth International conference on Parallel and Distributed Computing, Applications, and Technologies.