1. A method for scanning an image data file to determine the presence of a payload, comprising: a) automatically scanning, using a computer, an image data file to identify the values of bits in at least one fourth order or lower bit position, selected as a first bit position, and calculating and rendering as an output to a user said values of bits in said first bit position as attributable (or not) to continuous color blocks; b) automatically scanning, using a computer, an image data file to identify the values of bits in at least one fourth or lower bit position different from said first bit position and selected as a second bit position, and calculating and rendering as an output to a user said values of bits in said second bit position as attributable (or not) to contiguous color blocks; c) automatically scanning, using a computer, an image data file to identify the values of bits in at least one fourth or lower bit position different from said first or second bit position and selected as a third bit position, and calculating and rendering as an output to a user said values of bits in said third bit position as attributable (or not) to contiguous color blocks: and d) automatically calculating adjusted block difference percentages for each bit position and rendering as an output to a user the adjusted block difference percentages differentials to indicate the presence or absence of a payload in the image data file, wherein an alarm or event occurs to flag the image data file as suspicious for payload content.