-- PLEASE NOTE: If you are replying to this, consider pruning the list -- of cc's rather than crossposting replies wildly! Thanks. The LINX and several of its members have recently had to take action against an ISP that was using GRE tunneling between exchange points to appropriate the capacity of other ISPs. Although the offending party is now unlikely to repeat this abuse, we feel that this is an important vulnerabilty which could potentially be newly exploited by others elsewhere. We have created an advisory which describes details of the vulnerability, and how to detect and prevent it. This advisory can be found at http://www.linx.net/tunnel-advisory.txt Any questions are best referred to the authors listed in the advisory text. I would like to gratefully acknowledge the efforts of Lyndon Levesley and Alex Bligh at GX Networks among others in tracking down the abuse and creating this document. Keith Mitchell Chairman London InterNet Exchange keith@linx.org Geneva House, 3 Park Road Peterborough PE1 2UX United Kingdom Phone: +44 1733 705000 (fax 353929) Paul -- Paul Thornton, Network Engineer, London Internet Exchange Ltd. Tel: 07000 783797 Mobile: +44 467 372205