The change, which Immunity Security’s Kostya Kortchinsky said occurred about two months ago, represents a major departure from the design that has powered Skype for the past decade. Since its introduction in 2003, the network has consisted of “supernodes” made up of regular users who had sufficient bandwidth, processing power, and other system requirements to qualify. These supernodes then transferred data with other supernodes in a peer-to-peer fashion. At any given time, there were typically a little more than 48,000 clients that operated this way.
What’s more, the boxes are running a version of Linux using grsecurity, a collection of patches and configurations designed to make servers more resistant to attacks. In addition to hardening them to hacks, the Microsoft-hosted boxes are able to accommodate significantly more users.