Which of the following laws enacted in United States makes it illegal for an Internet Service Provider (ISP) to allow child pornography to exist on Web sites?

The Child Pornography Prevention Act (CPPA) of 1996 focused on criminalizing computer-generated and virtual child pornography but did not specifically impose reporting or hosting obligations on ISPs.

The PROTECT Act of 2003 strengthened child exploitation laws and addressed virtual child pornography but is broader in scope and does not specifically mandate ISP compliance for hosted web content in the way described.

The Protection of Children from Sexual Predators Act of 1998 (Public Law 105-314), commonly referred to as the Sexual Predators Act, requires Internet Service Providers to report any child pornography discovered on their systems to the National Center for Missing and Exploited Children (NCMEC). This law directly creates ISP legal liability for knowingly permitting child pornography to exist on hosted web services, which directly matches the scenario in the question.

The USA PATRIOT Act addresses terrorism-related surveillance and law enforcement powers and contains no provisions regarding ISP liability for child pornography on hosted platforms.