Patent ID: 8316446

Claim:
A method, comprising: intercepting at a Uniform Resource Locator (URL) filter module of a network device, an attempted download of a file from a URL; categorizing by the URL filter module of the network device the URL into a URL category according to a URL database; analyzing by a file type identifier module of the network device the file to determine its file type, wherein the file type of the file is determined by detecting one or more of a file type signature in the file and a file extension of the file, and identifying the file type of the file based on one or more of the file type signature detected in the file and the file extension of the file; and blocking or not blocking the attempted download according to a decision output of a blocking decision module of the network device which receives as inputs the URL category and the file type, wherein (i) if the URL category indicates a blacklist, the decision output is to block the download, (ii) if the URL category indicates a whitelist, the decision output is to allow the download, otherwise, the URL category specifies a URL content category indicating a type of content provided by the URL, and the decision output is based on whether files of said file type are permitted for URLs in the URL content category.