Title II of the Digital Millennium Copyright Act, the Online Copyright Infringement Liability Limitation Act, added Section 512 to the Copyright Act, providing four distinct safe harbors for online service providers. If the conduct of a service provider meets all the specific requirements of a safe harbor, the service provider will not be liable for monetary damages for copyright infringement, although injunctions to stop future infringement are possible.
In addition to the specifics of each safe harbor, there is the overall requirement that the service provider adopt a policy for terminating users who are repeat infringers, and that the service provider accommodate and not interfere with standard technological measures to protect copyrighted content.
The first safe harbor addresses "transitory digital network communications," the routing of messages across the Internet for users. The service provider is simply acting as a conduit for these messages, even though it may need to make temporary copies in its routers. In addition to the safe harbor, the Act imposes somewhat different injunction requirements for such service providers.
The second safe harbor addresses "system caching." At the time of the DMCA, it was common for a large service provider to cache copies of web pages that were being frequently accessed by its users, rather than retrieve a new copy each time, to minimize the traffic on the Internet backbone.
The third safe harbor, and the one most commonly associated with the Act, addresses "information residing on systems of networks at the direction of users." This is the "notice and takedown" provision, that says when properly notified of content alleged to be infringing, the service provider will remove it. That takedown can be challenged by the user, but any putback is delayed ten to fourteen business days, long enough for an infringement suit to be filed. To aid in filing such a suit, a copyright owner can subpoena a service provider for the identity of an alleged infringer.
The fourth safe harbor, addresses "information location tools" such as online directories or search engines.
Finally, there is a special limitation on liability for nonprofit educational institutions.