Wal-Mart apparently has an internal security operation that put's HP's ragtag private investigators to shame. It's called "Threat Research and Analysis Team". TechDirt and WSJ have all the details.
For instance, the company monitors the activity of vendors' computers
connected to its network, for things even as minute as whether they're surfing
porn, by using software that supposedly detects flesh tones when they're
displayed on screen.