Is the ruling on looting the same as the ruling on theft? Is it forbidden?

Both are forbidden by Sharia (definition). The thief (sariq): is one who takes money secretly from its secure place without any doubt [of right]. His hand is not to be cut off. As for the plundered (munnahib): he is one who takes money openly, relying on force and dominance. There is no cutting [of his hand] for him, based on the hadith (definition) narrated by Jabir, elevated [to the Prophet]: "There is no cutting for one who plunders." Warning against plundering has come in the hadith: "No one plunders a significant plunder, towards which people raise their eyes, while he is a believer."