Stop Online Piracy Act - Authorizes the Attorney General (AG) to seek a court order against a U.S.-directed foreign Internet site committing or facilitating online piracy to require the owner, operator, or domain name registrant, or the site or domain name itself if such persons are unable to be found, to cease and desist further activities constituting specified intellectual property offenses under the federal criminal code including criminal copyright infringement, unauthorized fixation and trafficking of sound recordings or videos of live musical performances, the recording of exhibited motion pictures, or trafficking in counterfeit labels, goods, or services.

Sets forth an additional two-step process that allows an intellectual property right holder harmed by a U.S.-directed site dedicated to infringement, or a site promoted or used for infringement under certain circumstances, to first provide a written notification identifying the site to related payment network providers and Internet advertising services requiring such entities to forward the notification and suspend their services to such an identified site unless the site's owner, operator, or domain name registrant, upon receiving the forwarded notification, provides a counter notification explaining that it is not dedicated to engaging in specified violations. Authorizes the right holder to then commence an action for limited injunctive relief against the owner, operator, or domain name registrant, or against the site or domain name itself if such persons are unable to be found, if: (1) such a counter notification is provided (and, if it is a foreign site, includes consent to U.S. jurisdiction to adjudicate whether the site is dedicated to such violations), or (2) a payment network provider or Internet advertising service fails to suspend its services in the absence of such a counter notification.

Requires online service providers, Internet search engines, payment network providers, and Internet advertising services, upon receiving a copy of a court order relating to an AG action, to carry out certain preventative measures including withholding services from an infringing site or preventing users located in the United States from accessing the infringing site. Requires payment network providers and Internet advertising services, upon receiving a copy of such an order relating to a right holder's action, to carry out similar preventative measures.

Provides immunity from liability for service providers, payment network providers, Internet advertising services, advertisers, Internet search engines, domain name registries, or domain name registrars that take actions required by this Act or otherwise voluntarily block access to or end financial affiliation with such sites.

Permits such entities to stop or refuse services to certain sites that endanger public health by distributing prescription medication that is adulterated, misbranded, or without a valid prescription.

Expands the offense of criminal copyright infringement to include public performances of: (1) copyrighted work by digital transmission, and (2) work intended for commercial dissemination by making it available on a computer network. Expands the criminal offenses of trafficking in inherently dangerous goods or services to include: (1) counterfeit drugs; and (2) goods or services falsely identified as meeting military standards or intended for use in a national security, law enforcement, or critical infrastructure application.

Increases the penalties for: (1) specified trade secret offenses intended to benefit a foreign government, instrumentality, or agent; and (2) various other intellectual property offenses as amended by this Act.

Directs the U.S. Sentencing Commission to review, and if appropriate, amend related Federal Sentencing Guidelines.

Requires the Secretary of State and Secretary of Commerce to appoint at least one intellectual property attache to be assigned to the U.S. embassy or diplomatic mission in a country in each geographic region covered by a Department of State regional bureau.