About BITS:
Background Intelligent Transfer Service
Background Intelligent Transfer Service is a component of Microsoft Windows 2000 and later iterations of the operating systems, which facilitates asynchronous, prioritized, and throttled transfer of files between machines using idle network bandwidth. It is most commonly used by recent versions of Windows Update, Microsoft Update, Windows Server Update Services, and System Center Configuration Manager to deliver software updates to clients, Microsoft's anti-virus scanner Microsoft Security Essentials to fetch signature updates, and is also used by Microsoft's instant messaging products to transfer files. BITS is exposed through the Component Object Model