this book constitutes the refereed proceedings of the 27th international conference on computer safety, reliability, and security, safecomp 2008, held in newcastle upon tyne, uk, in september 2008. the 32 revised full papers presented together with 3 keynote papers and a panel session were carefully reviewed and selected from 115 submissions. the papers are organized in topical sections on software dependability, resilience, fault tolerance, security, safety cases, formal methods, dependability modelling, as well as security and dependability.