Abstract: Preventing unauthorized data posts to a server hosting an information site, such as a site on the Web. A HASH value can be generated at a server computer hosting the information site using a message digest algorithm and appended, along with an additional data item present in the message used to generate the HASH value, to a data form in response to a request for the data form. In response to receiving a post containing data corresponding to data required by the data form, the server computer can determine if a HASH value and data item has been attached to the data post and if the HASH value is the same value as the HASH value sent with the form file. If data are posted without a correct HASH value, the data can be rejected by the server computer, preventing unauthorized posts of data to the information site.