is there any way for one to identify sites that use pixel tags, or to block those sites that use them? Also, for apps that have pixel tags in emails, can those be identified and blocked as well?
Pixel tags are just really images, so it’s difficult (it might be possible but I’m not sure) to identify them and distinguish them from other images on the page or in an email. You can generally screen them out by not allowing images to be downloaded in your email by default, and set your browser to disallow third-party cookies. I don’t think this will tell you which sites/emails are using them but it will help block them.
Some people call pixel tags ‘web bugs’ – at least I remember that name better from years ago. I use the Ghostery add-on in Firefox, but other people on this forum have found Ghostery for other browsers, or on Mac’s, to slow their system down too much.
Are you saying that if I get an email with images, the pixel tag could be in that email? And if I don’t permit pictures in my emails, if I decide to look at an email that looks interesting and I say “permit pictures”, the pixel tag then appears?
Aren’t these things a bit more intrusive than cookies in that most people dont even know about them, and they can pull more personal info off of your computer than a cookie can? Or am I misinformed?
They’re just images. They can’t “pull info” from your computer, and neither can a cookie. A cookie stores information sent by an HTTP server on your machine to be sent back to the same server on subsequent requests. That’s all they do.
Pixel tags are a way of getting around the fact that a web browser will not send cookies from one domain (say, wewantyourinfoez.com) to another domain (say example.com, which uses wewantyourinfoez.com as a third-party analytics provider.) They accomplish this by simply sending a cookie along with the image a file (a 1x1 image that you don’t see) so each time that image is loaded, the cookie is sent back. The image can then be hosted on a separate domain from the client site. The cookie contains a unique ID, so they can keep track of which pages a person visits on a site, in what order, and for how long, etc.
If they choose, a web site may elect to associate other information with that data, but that would be information you have to give them, like your name and demographic info, e.g. if it’s a web store.
If you don’t want these things, most ad filters (like AdBlock for Firefox or Chrome) will block them. The domains of the majority of advertising and analytics companies are well known, so it’s not hard.