OSINFO - Open Sources Information

In the previous blog post about the Iranian firewall, we explored macro level Iranian traffic engineering changes (showing that Iran cut all communication after the election and then slowly added back Internet connectivity over the course of several days). Like many other news reports and bloggers, we also speculated on Iran’s intent — how was the government manipulating Internet traffic and why?

Thanks to the cooperation of several ISPs in the region and Internet Observatory data, we can now do a bit better than speculate — we have pieced together a rough picture of what the Iranian government’s Internet firewall appears to be doing. The data shows that DCI, the Iranian state run telecommunications agency, has selectively blocked or rate-limited targeted Internet applications (either by payload inspection or ports).

I’ll step through several of these applications.

On average, Internet traffic is dominated by web pages (roughly 40-50% of all Internet traffic). And the vast majority of this web traffic (unless you happen to be Google or Facebook) goes into ISPs and the millions of associated end users (as opposed to traffic going out of a country or ISP). Iran is no exception.

The below graph shows web traffic (TCP port 80) into Iran over the days before and immediately after the election. Though the graph clearly shows a brief post-election outage followed by a decrease in web traffic, the Iranian web traffic was comparatively unaffected by Iran filter changes. Based on reports of Iran’s pre-existing Internet filtering capabilities, I’d speculate DCI did not require significant additional web filtering infrastructure.