The proliferation of Internet of Things has propelled the popularization of IEEE 802.15.4 standard. For the secure transmission of confidential data over 802.15.4, multiple encryption-based security techniques have been proposed in the literature. But these techniques do not ensure undetectable communication which is crucial in multiple scenarios like covert military operations. It is not sufficient enough to maintain the secrecy of the data using these techniques as it can arouse suspicion and even the encryption might be defeated by the adversary using advanced methods. For covert data communication, some steganographic techniques have been studied for 802.15.4 but unreliability makes it difficult to use for practical applications. In this paper, we propose a reliable method for covert data communication using redundancy in the direct spread spectrum sequences. We propose a secret acknowledgment and error detection method to ensure reliable communication in the covert channel. Results show that we can transfer confidential data reliably at a significant rate without considerably affecting the performance of primary data reception. © 2016 IEEE.