Quantifying Nations' Exposure to Traffic Observation and Selective Tampering

Almost all popular Internet services are hosted in a select set of countries, forcing other nations to rely on international connectivity to access them. We identify nations where traffic towards a large portion of the country is serviced by a small number of Autonomous Systems, and, therefore, may be exposed to observation or selective tampering by these ASes. We introduce the Country-level Transit Influence (CTI) metric to quantify the significance of a given AS on the international transit service of a particular country. By studying the CTI values for the top ASes in each country, we find that 34 nations have transit ecosystems that render them particularly exposed, where a single AS is privy to traffic destined to over 40% of their IP addresses. In the nations where we are able to validate our findings with in-country operators, our top-five ASes are 90% accurate on average. In the countries we examine, CTI reveals two classes of networks frequently play a particularly prominent role: submarine cable operators and state-owned ASes.