1. A method of processing an electronic file, the method comprising: identifying a portion of content data in the electronic file; determining if the identified portion of content data is passive content data having a fixed purpose or active content data having an associated function; if the identified portion of content data is determined to be passive content data, then: determining a file type or protocol of the portion of passive content data; and determining whether the portion of passive content data is to be re-generated by determining if the passive content data conforms to a predetermined data format comprising a set of rules corresponding to the file type or protocol; if the identified portion of content data is determined to be active content data, then analysing the portion of active content data to determine whether the portion of active content data is to be re-generated; and re-generating the portion of content data to create a re-generated electronic file, if the portion of content data is determined to be re-generated.