Sensing Barrier Pass Technique

According to Pain, Itachi and Kisame were able to enter Konohagakure undetected after Orochimaru's failed invasion because as a former member of Konohagakure's Anbu, Itachi knew how to pass through the barrier surrounding the village undetected.

Trivia

 * Koji Kashin was able to pass through the barrier without triggering the alarm, which surprised Delta.