On behalf of the Program Committee, it is our pleasure to present the p- ceedings of the 11th International Symposium on Recent Advances in Intrusion Detection (RAID 2008), which took place in Cambridge, Massachusetts, USA on September 15-17. The symposium brought together leading researchers and practitioners from academia, government and industry to discuss intrusion detection research and practice. There were six main sessions presenting full-?edged research papers (rootkit prevention, malware detection and prevention, high performance - trusion and evasion, web application testing and evasion, alert correlation and worm detection, and anomaly detection and network tra?c analysis), a session ofpostersonemergingresearchareasandcasestudies,andtwopaneldiscussions ("Government Investments: Successes, Failures and the Future" and "Life after Antivirus - What Does the Future Hold?"). The RAID 2008 Program Committee received 80 paper submissions from all over the world. All submissions were carefully reviewed by at least three independent reviewers on the basis of space, topic, technical assessment, and overallbalance.FinalselectiontookplaceattheProgramCommitteemeetingon May 23rd in Cambridge, MA. Twenty papers were selected for presentation and publication in the conference proceedings, and four papers were recommended for resubmission as poster presentations. As a new feature this year, the symposium accepted submissions for poster presentations,whichhavebeen publishedas extendedabstracts,reportingear- stageresearch,demonstrationofapplications,orcasestudies.Thirty-nineposters were submitted for a numerical review by an independent, three-person s- committee of the Program Committee based on novelty, description, and ev- uation. The subcommittee chose to recommend the acceptance of 16 of these posters for presentation and publication.