Abstract
The quantum secure direct communication (QSDC) protocol with a random basis and order is analysed and an effective attack, i.e. teleportation attack, is presented. An eavesdropper can obtain half of the transmitted secret bits with the help of this special attack. It is shown that quantum teleportation can be employed to weaken the role of the order-rearrangement encryption at least in a certain circumstance. Meanwhile, a possible improvement on this protocol is proposed, which makes it secure against this kind of attack.