Predatory play is one of several categories of play behavior exhibited by young kittens. Although the evolutionary function of predatory play is assumed to be to rehearse and sharpen predatory skills for use in later life, it is often interpreted by owners as blatant aggression. When a kitten has playmates (normally littermates) for company, predatory play aggression rarely becomes a problem, but when active, responsive company is lacking, the kittens may direct their playfulness towards their owners. Typically cats hide behind walls stalking and pouncing on approaching feet and ankles, inflicting scratches and minor bite wounds.
For more information, please read Predatory Aggression in Cats