The Motherboard has an extensive article on the teething issues faced by the U.S. Air Force in bringing the latest E-3G Block 40/45 online.
By U.S. Navy photo [Public domain], via Wikimedia Commons
A major deficiency was discovered during a three-week long Cooperative Vulnerability and Penetration Assessment in 2016. The flying branch discovered that the computer systems aboard the airborne early warning aircraft is susceptible to hacking.