Did They Read It?

There was a story on Talk of the Nation about DidTheyReadIt.com. It’s an email read-receipt service that uses web bugs to track when a recipient opens an email message. A web bug is an invisible image on a page that when loaded will send a unique URL request to a web server. For example:

http://didtheyreadit.com/index.php/worker?code=74dead4beef1cafe

DidTheyReadIt.com offers a free service with up to 5 messages per month and a paid service for a larger volume of messages. Messages flow through their SMTP servers to get “bugged” so you have to trust them to keep your content private.

Being able to tell whether someone has read your email is very useful. But clearly there are privacy concerns with this type of surreptitious tracking. Some spammers use web bugs for more nefarious purposes: to figure out which email addresses are “the good ones”. A web bug in a spam message can be used to find out when a spam message reaches a live email address. Obviously if you know that there’s someone on the other end of an email address you know you it may be worthwhile to send them more spam. And the fact that they opened the message indicates that they are interested in what you’re selling or that they don’t filter out spam or that your spam got past their spam filtering software. Further, there’s information leakage in web bugs: when a web bug pings the server it reports your IP address, the time of day, the type and version of your browser and possibly which operating system you use.