If a very crafty and nefarious Internet Roach decided to really come after you (not advertising, but with malice) could they launch a counterfeit fabrication that mimics the Bladeforums "HIT" to get by Guard Dog?
Of course.
Security is always that way. For every move, there is a counter-move. And for every counter-move, there is another counter-move.
This points out another really good reason to be very, very concerned about cookies. People other than those who created them can read them back. So, even if you trust the site that you're allowing to establish a cookie on your computer, you still need to be very concerned about what they're putting into that cookie. All someone needs to know is the name of the cookie file, and then they can read it too. Since sites use the same name for the cookie file on every PC on which they establish a cookie, that name is not hard to figure out.
Consider what I could do if I becomes aware that a certain online knife catalog site was trying to make shopping more convenient for its customers by making a cookie file on the customer's disk with the customer's name, address, and credit card data so that the customer doesn't have to enter that with every order. If I could figure out the name of the file they use (and that would be trivial, just visit the site myself and look for the new file on my disk) then I could add code to my site to check the disk of every person who visits my site to see if that cookie was there and, if so, to read it. My victims would never even know that I'd read the file. In fact, unless they're very computer savvy, they'd probably never figure out how I'd gotten ahold of their information.
And, if that's not enough to really get you worried, consider this: I can claim that any file on your computer is my cookie and, therefore, read and write it. What I can't do is get a directory of your disk. But, I often don't need that. Many programs these days store specific files in standardized locations. So, my site could simply claim that your browser history file is my cookie and read it. Now I know everywhere you've surfed in, typically, the last thirty days. I could claim your e-mail inbox as my cookie and read it.
Allowing unrestricted cookie access on your computer is a real risk to your security and privacy. So, I'm happy that I got Guard Dog. It's not perfect, I'm sure, but it does offer some protection.
I used to work in the military/industrial sector. The computers we used to do our work were simply not on the internet. There is no way to fully secure a computer with an internet connection. If we needed to use the internet, we had to go to another building (the building in which we worked did not have any network connection physically in it to simply elliminate the potential of any accidental connection) and use a different PC. The only way to get information from the internet to our working computer was to print it out and then type it back in, no cut-and-paste, no FTP, no e-mail it over, no putting it on a disk or tape, just print it out and type it back in.