Spam Filter E-mail - Email Spam Filter

Blank spam is spam lacking a payload advertisement. Often the message body is missing altogether, as well as the subject line. Still, it fits the definition of spam because of its nature as bulk and unsolicited email.

Blank spam may be originated in different ways, either intentional or unintentionally:

1. Blank spam can have been sent in a directory harvest attack, a form of dictionary attack for gathering valid addresses from an email service provider. Since the goal in such an attack is to use the bounces to separate invalid addresses from the valid ones, the spammer may dispense with most elements of the header and the entire message body, and still accomplish his or her goals.
2. Blank spam may also occur when a spammer forgets or otherwise fails to add the payload when he or she sets up the spam run.
3. Often blank spam headers appear truncated, suggesting that computer glitches may have contributed to this problem—from poorly-written spam software to shoddy relay servers, or any problems that may truncate header lines from the message body.
4. Some spam may appear to be blank when in fact it is not. An example of this is the VBS.Davinia.B email worm which propagates through messages that have no subject line and appears blank, when in fact it uses HTML code to download other files.

Image spam is an obfuscating method in which the text of the message is stored as a GIF or JPEG image and displayed in the email. This prevents text based spam filters from detecting and blocking spam messages. Image spam is currently used largely to advertise "pump and dump" stocks.[100]

Often, image spam contains nonsensical, computer-generated text which simply annoys the reader. However, new technology in some programs try to read the images by attempting to find text in these images. They are not very accurate, and sometimes filter out innocent images of products like a box that has words on it.

A newer technique, however, is to use an animated GIF image that does not contain clear text in its initial frame, or to contort the shapes of letters in the image (as in CAPTCHA) to avoid detection by OCR tools.