Unless the censor has total control over all Internet-connected computers, such as in North Korea or Cuba , total censorship of information is very difficult or impossible to achieve due to the underlying distributed technology of the Internet. Pseudonymity and data havens (such as Freenet ) protect free speech using technologies that guarantee material cannot be removed and prevents the identification of authors. Technologically savvy users can often find ways to access blocked content . Nevertheless, blocking remains an effective means of limiting access to sensitive information for most users when censors, such as those in China , are able to devote significant resources to building and maintaining a comprehensive censorship system. 
The seven-book Harry Potter series by has been a cult-favorite franchise since the first novel came out in 1997, leading to the release of eight movies based on the series and an amusement park inspired by the characters. Harry Potter has brought similar amount of controversy as it has obsession: the series was the most frequently challenged book in 2001 and 2002, before falling to second-most challenged book in 2003.  The ALA cites the reasons for censorship as "anti-family, occult/Satanism, religious viewpoint, violence",  but the American Civil Liberties Union of Texas's "Free People Read Freely" report also cited concerns over sexual content.  In one case in Lawrenceville, Georgia in 2007, a parent asked that the Harry Potter books be kept out of classrooms, suggesting that the novels promote the practice of witchcraft and contain violent content that is not suitable for her fifteen-year-old daughter to read as she was becoming inspired to try witchcraft like the characters do in the series.  School board attorney, Victoria Sweeney, presented evidence for why the novels should be kept in the classroom, noting that they encourage children's fascination with reading and explore themes such as good triumphing over evil.  The board ultimately unanimously decided to keep the books in the classroom since they had the potential to spark creativity and imagination, as well as a love for learning and reading.  In Lake Los Angeles, California , the school board in Wilsona School District passed a policy that prohibited books that "depict drinking alcohol, smoking, drugs, sex, including 'negative sexuality,' implied or explicit nudity, cursing, violent crime or weapons, gambling, foul humor and 'dark content.'"  These guidelines removed Harry Potter and the Half-Blood Prince from the school district's library because of mentions of these topics. The goal of the new policy was to make the library, which served students aged five to fifteen, more age-appropriate.  St. Joseph's School in Wakefield, Massachusetts allowed its students to select summer reading books in 2007, which led many students to read installments from the Harry Potter series. Once they returned to school, they found that these books had been removed from their library by Reverend Ron Barker, who did so because he believed that themes of sorcery and witchcraft did not belong in a Catholic school. While the Catholic Church has no clear standing on the books, the parents in the school district are divided over the Reverend's actions: some appreciate his efforts to protect students from witchcraft, while others wish the books were still accessible.