[Slick]

From the FAQ (but unfortunately not well placed):

A CI project is like a bank account. Available points are invested in projects (with interest).
Attacks subtract points from CI projects. This exchange happens each turn and new points go into
the CI project before your attacks come in. (Slick) Points added to CI in a turn are indeed used for defense in that turn if necessary. CI has no limit to the number of projects it can theoretically stop. (Imperator Fyron) For any given attack, if the defender has (greater
than or equal to) stored CI points, the attack will be blocked, and the corresponding amount of points are deducted from your stored CI projects, starting from the rightmost one and moving left. When you have no CI projects or no points stored in any of your CI projects, any subsequent completed attack project against your empire succeeds at 100% (Puppet Political Parties is 50%).

There is other info on Intel in the FAQ, check it out.

Slick.