Market Insider

What goes on inside Wall Street's secret backrooms

For every headline-grabbing foray by billionaire investors Carl Icahn or William Ackman, there are dozens more so-called activist investors the public never hears about. And this army of agitators is growing rapidly—and has a bulging arsenal of cash.

When activist investors show up in a stock, they often make headlines. Assets get sold, or in the high-profile case of Apple—there was a stock split, dividend hike and increased buyback.

But most of the time, they don't make headlines, and by some estimates, only about a third of the companies that are approached by activists ever make the overtures public.