Mechanisms for analyzing a structured file for malicious content are provided, comprising: parsing the structured file into a plurality of portions; selecting a selected portion of the portions; checking the selected portion to determine if at least one pre-condition is met; and in response to determining that the at least one pre-condition is met: decoding the selected portion to form a decoded portion; and checking the decoded portion to determine if it is malicious. In some embodiments: the at least one pre-condition can be changed; the structured file is a MICROSOFT OFFICE XML file; the selected portion is a file; the at least one pre-condition checks at least one attribute of the selected portion; decoding the selected portion comprises decompressing the selected portion; and/or checking the decoded portion to determine if it is malicious comprises checking whether a previously decoded portion of the structure file meets at least one condition.