Marketing companies have begun to embed invisible HTML "bugs" or "beacons" in their e-mail. Because these tiny one-pixel images must be retrieved from the sender's server when the message is opened, they can tell the sender when and how often a recipient looks at a message.
HTML makes browsers launch and the senders can place cookies on every PC that accepts the e-mail message with a bug. As a result, those cookies allow the sender to gather information like the recipient's IP address, the type of browser they use and the Web sites they visit, according to experts.
While the tracking software may be a boon for the senders because they can gauge the effectiveness of online ad campaigns -- perhaps using it to know exactly when to call a recipient at their desk -- it could also be exploited to transmit viruses or as a tool for spammers to gain hundreds of corporate e-mail addresses, industry experts warn.
"It's just a matter of time [before] someone [can] figure out how to use these things against people or corporations," said Sharon Ward, director of enterprise business applications at Hurwitz Group.
Ward said that because the software requires a query to the sender's server, these bugs could be used to send e-mail viruses. "It could be a tricky little Trojan Horse for getting viruses into unsuspecting people's e-mail. You just open up this message ... and it could send them off to everyone in your address book. You sort of think that if you're going to get an e-mail virus ... it's not going to come from a company trying to sell you a product."
Only two or three companies have developed this type of tracking software with a couple hundred marketers using it, Ward said.
In addition, spammers could use the bugs to get additional information about a company's e-mail addresses, said John Mozena, co-founder of the Coalition Against Unsolicited Commercial E-mail. Now, spammers can only guess that their e-mail has reached a person if it doesn't bounce back to them, he said. But because the Web bugs can confirm that the e-mail has actually been opened, spammers would know how a corporation builds e-mail addresses. They could then use software tools to automatically compile a list of common names in the template the company uses to devise e-mail addresses and lob more spam toward the company, possibly clogging mail servers, Mozena said.
"Because of the HTML bugs, you've confirmed to the sender that you've got the e-mail," Mozena said. "You've just made your address more valuable. It makes it more likely that your address will be sold or traded."
To help ward off the potential security pitfalls associated with the bugs, administrators should ensure security settings on the desktop are set so computers cannot run any unapproved script macros, Mozena said.
In addition, there are companies that specialise in blocking spam from entering the confines of a company's network. Brightmail offers a server-side solution that is designed to filter spam before it reaches mailboxes. Typically 30 per cent of all corporate e-mail is spam, according to Ken Schneider, CTO at Brightmail. While network administrators may seek to stem some of the problem by blocking cookies in the browser, if the mail package is programmed to accept cookies, then bugs could get to the user, he said.
Because the bugs allow marketers to confirm the validity of an e-mail address, they also may pose privacy concerns. Very few of the companies that use Web bugs detail how they use the software in their privacy polices, said Richard Smith, co-founder of The Privacy Foundation in the US. In addition to bugging e-mail, the software can also be used to track which sites a user visits on the Internet and to transmit information about a user, such as a postcode, from one Web site to another, he added.
"It just says flat out that we're being tracked on the Internet," he said.