What don't you follow? If 3 letter agencies had been given backdoor access by Cisco, why would the 3 letter agencies need to develop exploits that take advanta

What don't you follow? If 3 letter agencies had been given backdoor access by Cisco, why would the 3 letter agencies need to develop exploits that take advantage of flaws in the software? Cisco could have just added port knocking instead of adding additional accounts and logic errors and hoping nobody except the US govt finds it.