Steganalysis is a collection of techniques aiming at detecting whether some media carries secret information previously hidden using steganography. Detecting steganography is essential to fight against secret criminal communications or malware that is transmitted using covert steganographic channels. In the paper, an extensive analysis of Stegdetect is conducted by embedding random messages in 2000 JPEG images using JPHide steganography to establish the false-negative rate of the tool. The study concludes that the sensitivity parameter of Stegdetect is a key factor of the false-negative rates. The false-negative rates with Stegdetect are high for sensitivity values between 0.1 and 3.4. The best detection results for JPHide are obtained with a sensitivity value of 6.2. The paper concludes that the sensitivity parameter of Stegdetect needs to be adjusted carefully in forensic activities when many images are analyzed to reduce false-negative rates. [PERSON] and [PERSON] present Velody 2 [11], a new musical steganographic scheme for the MIDI format by modifying the velocity parameter considering constraints in capacity and security. The major drawback of most MIDI steganographic schemes is their lack of resilience against steganalysis since most existing methods leave traces that do not appear naturally in MIDI files. The proposed scheme is based on embedding information into the velocities of the note-on events to mimic the behavior of some available digital audio software suites. Data embedding is carried out by setting velocities to values within a narrow interval to be specified which removes potential mood swings in the velocity parameter of the music. The use of the technique is restricted to organ and harpischord music, which are naturally performed with constant or close to constant velocities, but the method can be used with little artificial effects on other types of music. Regarding resilience against steganalysis, Velody 2 is shown to leave very little traces and is comparable with the best MIDI steganographic methods in state-of-the-art methods. As audibility is concerned, it is shown that 30 listeners could not significantly guess which files contain embedded information. As far as embedding rate is concerned, Velody 2 outperforms the methods proposed in recent works. [PERSON] and [PERSON] [12] present a work on reversible and plausibly deniable covert channels OTP based on hash chains. A covert channel (CC) is an unforeseen communication channel in a system design that enables several actions related to cybercrime, such as information theft, barely detectable channels for commanding and controlling botnets, and secret criminal communications. The paper presents a covert channel between two devices where one device authenticates itself with [PERSON]'s OTP based on a cryptographic hash function. The proposed channel provides plausible deniability, i.e., the communicating parties can deny the existence of the covert channel and reversibility, i.e., the reconstruction of the original carrier message to the state before the steganographic data was embedded, and it can be applied in different contexts, such as traditional TCP/IP communications, Internet of Things (IoT) environments, blockchain-based systems, and local inter-process communications that rely on hash chains. Countermeasures to detect such a covert channel are also presented, but such detection is difficult because hash values appear to be random binary strings and deviations are hard to detect. Experimental results are presented to evaluate the channel's performance, to conduct statistical tests using the NIST suite, and to determine the channel's stealthiness (by running a test for matching hash values between legitimate and covert environments). The experiments show that the proposed channel might be detectable under realistic conditions only if no encryption is applied and authentication data are collected over a longer time span.