Editing Email spam (section)

==Spam techniques==

===Appending===
{{Main|Email appending}}

If a marketer has one database containing names, addresses, and telephone numbers of customers, they can pay to have their database matched against an external database containing email addresses. The company then has the means to send email to people who have not requested email, which may include people who have deliberately withheld their email address.<ref>{{cite web|url=http://www.cluelessmailers.org/articles/2008-01-19-gettingitwrong.html |archive-url=https://archive.today/20130414114546/http://www.cluelessmailers.org/articles/2008-01-19-gettingitwrong.html |url-status=dead |archive-date=April 14, 2013 |title=Getting it Wrong: Corporate America Spams the Afterlife |publisher=Clueless Mailers |author=Bob West |date=January 19, 2008 |access-date=2010-09-23 }}</ref>

===Image spam===
{{Main|Image spam}}

[[Image spam]], or image-based spam,<ref name="Image Based spam name">Giorgio Fumera, Ignazio Pillai, Fabio Roli,{{cite journal|url=http://jmlr.csail.mit.edu/papers/v7/fumera06a.html|title=Spam filtering based on the analysis of text information embedded into images|journal=Journal of Machine Learning Research|year=2006|volume=7|issue=98|pages=2699–2720|last1=Fumera|first1=Giorgio|access-date=2013-03-19|archive-date=2015-02-21|archive-url=https://web.archive.org/web/20150221103301/http://jmlr.csail.mit.edu/papers/v7/fumera06a.html|url-status=live}} Journal of Machine Learning Research (special issue on Machine Learning in Computer Security), vol. 7, pp. 2699-2720, 12/2006.</ref><ref name="Image Based spam name 2">Battista Biggio, Giorgio Fumera, Ignazio Pillai, Fabio Roli,{{cite journal|title=A survey and experimental evaluation of image spam filtering techniques| doi=10.1016/j.patrec.2011.03.022 | volume=32|issue=10|journal=Pattern Recognition Letters|pages=1436–1446|year=2011|last1=Biggio|first1=Battista|last2=Fumera|first2=Giorgio|last3=Pillai|first3=Ignazio|last4=Roli|first4=Fabio| bibcode=2011PaReL..32.1436B }} Volume 32, Issue 10, 15 July 2011, Pages 1436-1446, ISSN 0167-8655.</ref> is an obfuscation method by which 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 was reportedly used in the mid-2000s to advertise "[[pump and dump]]" stocks.<ref name="techtarget">{{cite news|author=Eric B. Parizo|title=Image spam paints a troubling picture|url=http://searchsecurity.techtarget.com/originalContent/0,289142,sid14_gci1204126,00.html|publisher=Search Security|date=2006-07-26|access-date=2007-01-06|archive-date=2007-02-24|archive-url=https://web.archive.org/web/20070224152029/http://searchsecurity.techtarget.com/originalContent/0%2C289142%2Csid14_gci1204126%2C00.html|url-status=live}}</ref>

Often, image spam contains nonsensical, computer-generated text which simply annoys the reader. However, new technology in some programs tries to read the images by attempting to find text in these images. These programs are not very accurate, and sometimes filter out innocent images of products, such as 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 [[optical character recognition]] tools.

===Blank spam===
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.<ref>{{cite web|url=http://www.cnet.com/news/dealing-with-blank-spam/|title=Dealing with blank spam|website=CNET|date=September 2, 2009|access-date=August 17, 2015|archive-date=September 23, 2015|archive-url=https://web.archive.org/web/20150923230039/http://www.cnet.com/news/dealing-with-blank-spam/|url-status=live}}</ref>

Blank spam may be originated in different ways, either intentional or unintentionally:
# 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, spammers may dispense with most elements of the header and the entire message body, and still accomplish their goals.
# Blank spam may also occur when a spammer forgets or otherwise fails to add the payload when they set up the spam run.
# Often blank spam headers appear truncated, suggesting that computer glitches, such as [[software bugs]] or other may have contributed to this problem—from poorly written spam software to malfunctioning relay servers, or any problems that may truncate header lines from the message body.
# Some spam may appear to be blank when in fact it is not. An example of this is the VBS.Davinia.B email worm<ref>{{cite web|url=http://www.symantec.com/security_response/writeup.jsp?docid=2001-020713-3220-99|title=Symantec|publisher=[[Broadcom#Symantec enterprise security|Symantec]]|access-date=2012-12-10|archive-date=2012-11-20|archive-url=https://web.archive.org/web/20121120184413/http://www.symantec.com/security_response/writeup.jsp?docid=2001-020713-3220-99|url-status=dead}}</ref> which propagates through messages that have no subject line and appears blank, when in fact it uses HTML code to download other files.

===Backscatter spam===
{{Main|Backscatter (email)}}
Backscatter is a side-effect of email spam, [[computer viruses|viruses]], and [[computer worm|worms]]. It happens when email servers are misconfigured to send a bogus [[bounce message]] to the [[envelope sender]] when rejecting or quarantining email (rather than simply rejecting the attempt to send the message).

If the sender's address was forged, then the bounce may go to an innocent party. Since these messages were not solicited by the recipients, are substantially similar to each other, and are delivered in bulk quantities, they qualify as unsolicited bulk email or spam. As such, systems that generate email backscatter can end up being listed on various [[DNSBL]]s and be in violation of [[internet service provider]]s' [[Terms of Service]].