Despite the Chee's outward defences there really isn't much to confine Jarvis inside. The Pemalites were trusting in the extreme and rather than 'security' Erek has powerful repair programs - which he's tweaked and repurposed to enable his hacking and sabotage. Jarvis being off-limits to their attention, he'll find he has access to Erek's sensors.

In fact there's only two notable barriers aside from Erek's own activities: a single, impregnable set of codes that runs through the Chee's functions like a frame of steel wire, and an array of weak programs set up around his memory archives, an attempt to control their access.

Erek looks around the grey walls and the dim consoles, then heads out to check the rest of the labs, the ship's deck humming under his feet. His hologram shifts as he steps through the door.

We should ensure that nothing else from your systems remains here.