Whom is Egypt fighting against in Sinai?

Egypt's al-Masry al-Youm reports on the Egyptian army's operation in Sinai. After going through this lengthy article, it's not clear to me just whom the Egyptians are fighting. One thing seems certain: Letting them send more troops and equipment into Sinai in violation of the Camp David treaty is asking for trouble. Moussa al-Delh, a member of Sinai’s influential Tarabeen tribe, was a fugitive