This chapter studies the establishment of DNA databases and their relevance at two levels. On the one hand, as a basis for criminal investigation, they contribute to the protection of the public against potentially criminal behavior. In our societies, mass violence is not a sporadic occurrence and knowledge. When DNA databases allow for preventive action, they may be synonymous with safety. On the other hand, DNA databases pose deeper problems, such as a felon's data are still personal data and as such need to be protected. Any violation of this right is against the law. Therefore, a society that wants to be lawfully protected must first protect. The study is focused on Spanish and Portuguese statutes enforced in 2007 and 2008, respectively, as well as on doctrine and jurisprudence produced in both countries and intended to strengthen cyberspace security and to guarantee access to information.