The openness of the Web allows any user to access any type of information easily at any time and anywhere. However, with function of easy access for useful information, internet has dysfunctions of providing users with harmful contents indiscriminately. Some information, such as adult content, is not appropriate for children. To protect children from these harmful contents, many filtering softwares are developed. However, these softwares can not prevent harmful contents, perfectly, because of some limitations. In this paper, we analyze existing eleven filtering softwares and state the limitation of these softwares. Furthermore, we propose requirements for new filtering software which overcomes the limitations, and describe framework of the new software..