1. A method of detecting spam images in electronic mail, the method comprising: obtaining one or more known spam e-mails; obtaining and extracting known spam images from the known spam e-mails; compressing the extracted known spam images into a common representation having a common size and color palette using a lossy compression function; using the compressed known spam images to create a corpus of compressed known spam images; extracting images embedded in a subject electronic mail message; compressing the extracted images embedded in the subject electronic mail message into a common representation having the common size and color palette using a lossy compression function; determining if the compressed forms of the extracted images embedded in the subject electronic mail message are identical to the compressed form of any of the extracted known spam images in the corpus of known spam images; and signaling the subject electronic mail message as embedding a spam image on the basis of a compressed form of an extracted image extracted from the subject electronic mail message being determined to be identical to the compressed form of a known spam image.