Laser beam intrusion detection systems, iris scanners and customized access cards are just some of the controls that Google uses to protect its data centers.
Other measures include dual authentication systems, vehicle-access barriers, high-resolution cameras, metal detectors, perimeter fencing and so-called circle-lock portals to prevent tailgaters from entering protected areas by following too closely behind someone with a valid access card. Access to the actual data center floors itself is often only possible through a security corridor featuring multifactor authentication systems.
Read more at eWeek
