Shares of Palo Alto Networks (PANW) have lately been "just kind of unstoppable," CNBC's Jim Cramer said Monday.

"Those who are looking for bull markets — of which most have been elusive of late, except maybe the health insurers — look at cybersecurity. You have Palo Alto, which, I think, is the king of it," Cramer said on "Squawk on the Street."