MOR: Monitoring and Measurements through the Onion Router

A free and easy to use distributed monitoring and measurement platform would be valuable in several applications: monitoring network or server infrastructures, performing research experiments using many ISPs and test nodes, or checking for network neutrality violations performed by service providers. In this paper we present MOR, a technique for performing distributed measurement and monitoring tasks using the geographically diverse infrastructure of the Tor anonymizing network. Through several case studies, we show the applicability and value of MOR in revealing the structure and function of large hosting infrastructures and detecting network neutrality violations. Our experiments show that about 7.5% of the tested organizations block at least one popular application port and about 5.5% of them modify HTTP headers.