>> guest: a zero day is a full ability, so sergei ivanov and jody exploit the vulnerability is executable and software that the vendor does know about and therefore, there's no patch available yet zero day exploit is the malicious code that hackers developed to attack that hole and attained access to the system and install a virus or a trojan horse or something else on the system. i described the equivalent of a burglar using a crowbar to open a window and again into to house the that's what a zero day exploit is. >> host: and wired reporter kim zetter is the author of this book, "countdown to zero day." thanks for being with the. >> guest: thanks for having me. >> every weekend tv offers programmiprogrammi ng focus on nonfiction authors and books. keep watching for more on c-span2 and watch any of our past programs online at booktv.org. >> while in corpus christi we spoke with robert worcester author of american military frontiers should force the varied roles the military has played in america's western expansion. >> when people think of the military in the american west they think of f