Web bugs are images in e-mail that confirm that your e-mail address is real, and you have just read the e-mail by downloading the image.

You might not see them at times as they can be 1x1, and transparent. Other times they appear as any ordinary image, but the one thing you don't see all the time is the string they send when requesting the image from the server. It could be some random number assigned to your address on the server, or it could be obvious with your e-mail address in the request.

These are easily blocked by a firewall that allows you to control the ports per application. Others might not allow this, and only allow/block/drop the packets from that application so you would have to allow the web bug requests along with the request to send/receive your e-mail. The simplest way is to allow your pop3(tcp 110), smtp(tcp 25), and imap(tcp 143) ports if necessary. Most of the time web bugs use port tcp 80, but this port can vary so securing which ports the programs use is the easiest route. What can complicate this is software proxies, here you just make sure that your mail application is not allowed to run through your software proxy if possible.

Many programs allow you to turn off this feature. In Outlook Express you can force your messages to appear in text in your options, and that will take care of web bugs if you have not also done the firewall route.

Answer submitted by: Blitzenzeus