One thing I should note about all the Chaos spies is that the<em>Kobras Aquairre</em>and the<em>Reliquary of Alexander</em>are pretty immune to chaos infiltrators, due to their distinctive shipboard culture and intense brainwashing respectively.<br/><br/>Currently, the<em>Everest</em>is fairly vulnurable to spies, and will likely be so for a long time, unless you're very successful in establishing colonies of people who can be trusted.  Naturally, the Tau might be able to help indoctrinate your crews to eliminate heresy, and attaching an Inquistor to the fleet will eliminate the risk of heresy entirely.  (this is another area where not having a missionary is a bit of a drag on your efforts, though putting creed components in your fleet will also supress shipboard heresy)