In the United States, many of the rules and regulations concerning Internet copyright laws are spelled out in the Digital Millennium Copyright Act, also known as the DMCA. The Digital Millennium Copyright Act protects Internet service providers, also known as ISPs, from liability due to copyright infringement by ISP users. The DMCA states that ISPs may be immune from liability if the ISP removes or blocks infringing content after being notified of a copyright violation. Often, sending a cease and desist letter and/or notifying a ISP of infringing content is enough to settle a copyright infringement claim. In other cases, it may be necessary to sue the infringer in order to stop a copyright infringement. Internet copyright laws generally protect original creative work, and while it is not necessary to obtain an official copyright registration in order for a work to be copyrighted, registering a work does offer extra protection in the event of infringement.