Detecting Stepping-Stone Intruders with Long Connection Chains

It is generally agreed that there is no valid reason to use a long connection chain for remote login such as SSH connection. Most of the stepping-stone detection algorithms installed on a host were designed to protect the victim of a third party downstream from where the algorithm is running. It is much more important for a host to protect itself from being a victim. This project uses an approximated round-trip time to distinguish a long connection chain from a short one. Several measures were studied to distinguish long chains from short ones. An estimated roundtrip time was defined to measure the chain length. Preliminary result suggests shows that the proposed algorithm can distinguish long connection chains from short ones with relatively low false rate.