How Spammers use web bugs to determine if email is read
The following information is excerpted from The Privacy Foundation web page.
About the Privacy Foundation
Mary Reed Building
2199 S. University Blvd.
Denver, CO 80208
The Privacy Foundation exists to educate the public, in part by conducting
research into communications technologies and services that may pose a
threat to personal privacy.
1. What exactly is a Web Bug? http://www.privacyfoundation.org/resources/webbug.asp
A Web bug is a graphic on a Web page or in an Email message that is designed to monitor who is reading the Web page or Email message. Web bugs are often invisible because they are typically only 1-by-1 pixel in size. They are represented as HTML IMG tags.
2. Why are Web Bugs invisible on a page?
To hide the fact that monitoring is taking place.
10. What kinds of uses does a Web bug have in an Email message?
A Web bug can be used to find out if a particular Email message has been read by someone and if so, when the message was read. A Web bug can provide the IP address of the recipient if the recipient is attempting to remain anonymous. Within an organization, A Web bug can give an idea how often a message is being forwarded and read.
11. Why are Web bugs used in "junk" Email messages?
To measure how many people have viewed the same Email message in a marketing campaign. To detect if someone has viewed a junk Email message or not. People who do not view a message are removed from the list for future mailings. To synchronize a Web browser cookie to a particular Email address. This trick allows a Web site to know the identity of people who come to the site at a later date.
14. What do Web bugs in Email messages look like?
Email Web bugs are represented as 1-by-1 pixel IMG tags just like Web bugs for Web pages. However, because the sender of the message already knows your Email address, they also include the Email address in the Web bug URL. The Email address can be in plain text or encrypted. For example, here are two Web bugs sent to me in junk Email messages:
img width='1' height='1' src="http://www.m0.net/m/logopen02.asp? vid=3&catid=370153037&email=SMITHS %40tiac.net" alt=" ">
IMG SRC="http://email.bn.com/cgi-bin/flosensing? x=ABYoAEhouX">