Our site is pittcon.org
It's not from downloading anything, they're just visiting the site, or trying to log-in to register for our conference.
From what everyone that calls has been saying, when they go to the site, they get a security error on their browser screen. They can't even see our site. Only Chrome users seem to be able to click "advanced" then show the site anyway. IE and Firefox users can't get past the security warning.