Illumio
The security company that assumes the attacker is already inside and simply wants to stop them getting any further.
Andrew Rubin and PJ Kirner founded Illumio in Sunnyvale in 2013. Its product does microsegmentation without touching the network: an agent on every server or workstation drives the host's own firewall, and a central service works out which flows are actually needed. Everything else is closed, so a compromised machine can't reach the rest of the data centre.
For years it was a hard sell — segmentation is dull and requires knowing what talks to what. The ransomware wave changed the maths, because the expensive breaches are rarely about the first foothold and almost always about the lateral movement afterwards. The company now markets itself as "zero trust segmentation".