From Paterva Wiki
This transform determines the Autonomous System (AS) number of the supplied network. It gets this by looking in up on Serversniff. This is useful for determining if two (or more) networks are related. If two networks are in the same AS (e.g. have the same AS number) we can say they are at least loosely routed to the same destination. If the networks belongs to an organization (as opposed to belonging to an ISP that is splitting the network into smaller networks and leasing them to clients) we get a good indication that both networks belong to the same organization. For more information about AS numbers see the Wikipedia entry here .