Which detection method would not detect a mismatch between the file name and its content type?

The detection method that would not identify a mismatch between the file name and its content type is checking the file extension. This approach relies solely on the naming convention of the file, which can often be misleading or altered. File names can be easily modified without any corresponding change to the actual content of the file. For instance, a file named "document.pdf" could contain a completely different type of data, such as executable code or an image, which would only be evident upon further inspection.

In contrast, other methods like checking the HTTP content type or inspecting the file signature are more robust and directly analyze the characteristics of the file's actual content rather than just its name. Checking the HTTP content type examines the headers sent with the file transfer, which typically declare the true format of the file. Detecting apparent data type involves analyzing the file's content to determine its actual type based on patterns or structures within the data.

Thus, only evaluating the file extension is insufficient in ensuring that the stated file type and format accurately match, making it the most ineffective method for this purpose.