def hash_prefix_list_checksum(self, threat_list):
        q = '''SELECT value FROM hash_prefix
                WHERE threat_type=? AND platform_type=? AND threat_entry_type=?
                ORDER BY value
        '''
        params = [threat_list.threat_type, threat_list.platform_type, threat_list.threat_entry_type]
        with self.get_cursor() as dbc:
            dbc.execute(q, params)
            all_hashes = b''.join(bytes(h[0]) for h in dbc.fetchall())
            checksum = hashlib.sha256(all_hashes).digest()
        return checksum