In an embodiment, a computer system comprises one or more computer processors configured with a message transfer application; a message transfer/vision processing (MT/VP) interface coupled to the one or more computer processors and interposed between the message transfer application and a vision processing computer, wherein the MT/VP interface performs operations comprising: extracting risk indicator data from a message that is in transit to a recipient computer on a computer network; in response to the risk indicator data matching a message risk criterion, transmitting an image address for an image of interest coupled to the message or the image of interest to the vision processing computer; receiving, from the vision processing computer, a label that semantically describes visual content of the image of interest; using the label, querying a set of correlation data to determine a reference address that is associated with the label; in response to the image address matching the reference address, transmitting the message to the recipient computer; in response to the image address not matching the reference address, modifying, delaying or blocking the transmitting of the message to the recipient computer.