Direct copyright infringement occurs when someone exercises the exclusive rights of a copyright holder without authorization, such as copying or distributing a work. Indirect infringement includes contributory infringement, which involves knowingly inducing or contributing to direct infringement, and vicarious infringement, which involves having the ability to control infringement and receiving financial benefit from it. Defenses include fair use, lack of copyright validity, and safe harbors for libraries. Remedies for infringement include damages, attorney's fees, injunctions, and in rare cases criminal penalties.