According to a recent article in Yediyot Ahronot, the IDF's Homefront Command and Gaza Division have decided that the "Code Red" warnings will also be used for terrorists infiltrating Israel through tunnels.
Up to now, "Code Red" alerts have only been used for rocket attacks.
In addition to the auditory warning, security coordinators will receive relevant instructions and residents will receive text messages with the note "Due to a terrorist infiltration, residents are requested to remain indoors and to extinguish the lights until further notice." The SMS will be sent in order to clarify that the "Code Red" referred to a tunnel attack and not a rocket.
The newspaper quoted a security official as saying, "The siren is a further measure to make civilians aware that something is going on. Of course, the siren will also operate normally in the case of rocket attacks. Civilians must understand that not every siren will signify a terrorist invasion."