The language is very vivid here, rather like a vessel being shaken about in a great storm at sea. Paul is concerned that their minds should be protected so that they are not tempest-tossed by somebody claiming to be speaking by the Holy Spirit.
Our defence against all attacks based on false reports or false doctrine is to hold on to the Scripture which God has given us for this very purpose. We should expect such attacks to come and not be taken by surprise for Satan will not leave us to live out the rest of our Christ lines in peace.