WAFP is a Web Application Finger Printer written in ruby using a SQLite3 DB.
webapplicationfingerprinter - Project Hosting on Google Code
How it works? -- WAFP fetches the files given by the Finger Prints from a webserver and checks if the checksums of those files are matching to the given checksums from the Finger Prints. This way it is able to detect the detailed version and even the build number of a Web Application. In detail? -- A Web Application Finger Print consits of a set of relative file locations in conjunction with their md5sums. It is made based on a production or example installation of a Web Application or just out of an extracted Web Application install files tarball.