Child pornography is prohibited by federal statutes, which provide for civil and criminal penalties for its production, advertising, possession, receipt, distribution, and sale. Defined by statute as the visual depiction of a minor—a person under 18 years of age—engaged in sexually explicit conduct, child pornography is unprotected by the First Amendment, as it is intrinsically related to the sexual abuse of children. In the Child Pornography Prevention Act of 1996, Congress sought to prohibit images that are or appear to be “of a minor engaging in sexually explicit conduct” or are “advertised, promoted, presented, described, or distributed in such a manner that conveys the impression that the material is or contains a visual depiction of a minor engaging in sexually explicit conduct.” In 2002, the Supreme Court struck down this legislative attempt to ban “virtual” child pornography in Ashcroft v. The Free Speech Coalition, ruling that the expansion of the act to material that did not involve and thus harm actual children in its creation is an unconstitutional violation of free speech rights. According to government officials, this ruling may increase the difficulty of prosecuting those who produce and possess child pornography. Defendants may claim that pornographic images are of “virtual” children, thus requiring the government to establish that the children shown in these digital images are real. Historically, pornography, including child pornography, tended to be found mainly in photographs, magazines, and videos. With the advent of the Internet, however, both the volume and the nature of available child pornography have changed significantly. The rapid expansion of the Internet and its technologies, the increased availability of broadband Internet services, advances in digital imaging technologies, and the availability of powerful digital graphic programs have led to a proliferation of child pornography on the Internet. According to experts, pornographers have traditionally exploited—and sometimes pioneered—emerging communication technologies—from the dial-in bulletin board systems of the 1970s to the World Wide Web—to access, trade, and distribute pornography, including child pornography. Today, child pornography is available through virtually every Internet technology (see table 1). Among the principal channels for the distribution of child pornography are commercial Web sites, Usenet newsgroups, and peer-to-peer networks. Web sites. According to recent estimates, there are about 400,000 commercial pornography Web sites worldwide, with some of the sites selling pornographic images of children. The child pornography trade on the Internet is not only profitable, it has a worldwide reach: recently a child pornography ring was uncovered that included a Texas-based firm providing credit card billing and password access services for one Russian and two Indonesian child pornography Web sites. According to the U.S. Postal Inspection Service, the ring grossed as much as $1.4 million in just 1 month selling child pornography to paying customers. Usenet. Usenet newsgroups also provide access to pornography, with several of the image-oriented newsgroups being focused on child erotica and child pornography. These newsgroups are frequently used by commercial pornographers who post “free” images to advertise adult and child pornography available for a fee from their Web sites. Peer-to-peer networks. Although peer-to-peer file-sharing programs are largely known for the extensive sharing of copyrighted digital music, they are emerging as a conduit for the sharing of pornographic images and videos, including child pornography. In a recent study by congressional staff, a single search for the term “porn” using a file-sharing program yielded over 25,000 files. In another study, focused on the availability of pornographic video files on peer-to-peer sharing networks, a sample of 507 pornographic video files retrieved with a file-sharing program included about 3.7 percent child pornography videos. Table 2 shows the key national organizations and agencies that are currently involved in efforts to combat child pornography on peer-to-peer networks. The National Center for Missing and Exploited Children (NCMEC), a federally funded nonprofit organization, serves as a national resource center for information related to crimes against children. Its mission is to find missing children and prevent child victimization. The center’s Exploited Child Unit operates the CyberTipline, which receives child pornography tips provided by the public; its CyberTipline II also receives tips from Internet service providers. The Exploited Child Unit investigates and processes tips to determine if the images in question constitute a violation of child pornography laws. The CyberTipline provides investigative leads to the Federal Bureau of Investigation (FBI), U.S. Customs, the Postal Inspection Service, and state and local law enforcement agencies. The FBI and the U.S. Customs also investigate leads from Internet service providers via the Exploited Child Unit’s CyberTipline II. The FBI, Customs Service, Postal Inspection Service, and Secret Service have staff assigned directly to NCMEC as analysts. Two organizations in the Department of Justice have responsibilities regarding child pornography: the FBI and the Justice Criminal Division’s Child Exploitation and Obscenity Section (CEOS). The FBI investigates various crimes against children, including federal child pornography crimes involving interstate or foreign commerce. It deals with violations of child pornography laws related to the production of child pornography; selling or buying children for use in child pornography; and the transportation, shipment, or distribution of child pornography by any means, including by computer. CEOS prosecutes child sex offenses and trafficking in women and children for sexual exploitation. Its mission includes prosecution of individuals who possess, manufacture, produce, or distribute child pornography; use the Internet to lure children to engage in prohibited sexual conduct; or traffic in women and children interstate or internationally to engage in sexually explicit conduct. Two other organizations have responsibilities regarding child pornography: the Customs Service (now part of the Department of Homeland Security) and the Secret Service in the Department of the Treasury. The Customs Service targets illegal importation and trafficking in child pornography and is the country’s front line of defense in combating child pornography distributed through various channels, including the Internet. Customs is involved in cases with international links, focusing on pornography that enters the United States from foreign countries. The Customs CyberSmuggling Center has the lead in the investigation of international and domestic criminal activities conducted on or facilitated by the Internet, including the sharing and distribution of child pornography on peer-to-peer networks. Customs maintains a reporting link with NCMEC, and it acts on tips received via the CyberTipline from callers reporting instances of child pornography on Web sites, Usenet newsgroups, chat rooms, or the computers of users of peer-to-peer networks. The center also investigates leads from Internet service providers via the Exploited Child Unit’s CyberTipline II. The U.S. Secret Service does not investigate child pornography cases on peer-to-peer networks; however, it does provide forensic and technical support to NCMEC, as well as to state and local agencies involved in cases of missing and exploited children. Child pornography is easily shared and accessed through peer-to-peer file- sharing programs. Our analysis of 1,286 titles and file names identified through KaZaA searches on 12 keywords showed that 543 (about 42 percent) of the images had titles and file names associated with child pornography images. Of the remaining files, 34 percent were classified as adult pornography, and 24 percent as nonpornographic (see fig. 1). No files were downloaded for this analysis. The ease of access to child pornography files was further documented by retrieval and analysis of image files, performed on our behalf by the Customs CyberSmuggling Center. Using 3 of the 12 keywords that we used to document the availability of child pornography files, a CyberSmuggling Center analyst used KaZaA to search, identify, and download 305 files, including files containing multiple images and duplicates. The analyst was able to download 341 images from the 305 files identified through the KaZaA search. The CyberSmuggling Center analysis of the 341 downloaded images showed that 149 (about 44 percent) of the downloaded images contained child pornography (see fig. 2). The center classified the remaining images as child erotica (13 percent), adult pornography (29 percent), or nonpornographic (14 percent). These results are consistent with the observations of NCMEC, which has stated that peer-to-peer technology is increasingly popular for the dissemination of child pornography. However, it is not the most prominent source for child pornography. As shown in table 3, since 1998, most of the child pornography referred by the public to the CyberTipline was found on Internet Web sites. Since 1998, the center has received over 76,000 reports of child pornography, of which 77 percent concerned Web sites, and only 1 percent concerned peer-to-peer networks. Web site referrals have grown from about 1,400 in 1998 to over 26,000 in 2002—or about a nineteenfold increase. NCMEC did not track peer-to-peer referrals until 2001. In 2002, peer-to-peer referrals increased more than fourfold, from 156 to 757, reflecting the increased popularity of file-sharing programs. Juvenile users of peer-to-peer networks face a significant risk of inadvertent exposure to pornography when searching and downloading images. In a search using innocuous keywords likely to be used by juveniles searching peer-to-peer networks (such as names of popular singers, actors, and cartoon characters), almost half the images downloaded were classified as adult or cartoon pornography. Juvenile users may also be inadvertently exposed to child pornography through such searches, but the risk of such exposure is smaller than that of exposure to pornography in general. To document the risk of inadvertent exposure of juvenile users to pornography, the Customs CyberSmuggling Center performed KaZaA searches using innocuous keywords likely to be used by juveniles. The center image searches used three keywords representing the names of a popular female singer, child actors, and a cartoon character.