Take a quick second and Google / Bing for the words “Privdog” or “Superfish.”
In a nutshell, these applications install a certificate, which your computers then trust. Then because of that, the chain of trust is broken, and the bad guys can use that as an attack into your systems.
Good news: You can keep vigilent and wipe these evil certificates off your network on all PCs, all at once, using PolicyPak and Group Policy or SCCM or whatever system you use. Here’s Sal from Tech Support with his how to video: