Traffic distribution systems act as brokers that both buy and sell traffic from one site to another. They ad value by filtering traffic based on a user’s browser, IP address, geography anduser agent data. When a user clicks on a link that is part of a TDS chain they aresilently redirected to a malicious web pagebased on their profile.
TDS systems are notorious for aiding criminals in distributing web-based malware via exploit kits and fake downloads.
Source: threatpost.com