Although it's not something new, network administrators are still facing old pro blems. One of these problems is to be ab le to detect rogue and/or fake access po ints in their networks and surroundings. The solutions available are mostly comme rcial and/ or proprietary, but still no open-source tool. Now there is: Beholder . The talk will include a brief introduc tion on the general state of the commerc ial WIDS and will be mostly focused on t he Beholder project. Beholder is an C la nguage opensource tool available (for no w) for linux platforms, it can be used f or whatever 802.11 technology the nic ca rd supports and it isn't driver dependen t, run in all available linux wifi drive r. Nelson Murilo has been a Network Securit y Analyst since 1992. He is the author o f two network security books in Portugue se and a regular contributor of Brazilia n Computer Emergency Response Team publi shed papers (security guides and technic al papers). Nelson is the author and co- author of open source security tools lik e chkrootkit and Btsearch. Regular speak er in Brazil and international conferenc es and is one of the organizers of a Bra zilian security conference YSTS (you sh0 t the sheriff).