Firewalls, intrusion detection systems, and even encryption haven't kept hackers out of hoards of data like the ones stolen in the catastrophic breaches of Equifax or Yahoo. But now, some Silicon Valley firms are trying a deeper approach, building security into the basic design of how data moves between a company's servers. The method aims not to seal intruders out of sensitive systems, but to tighten the rim of the cookie jar around their wrist, trapping their grabby hands inside.