# Detecting Malicious Devices in IPSEC Traffic with IPv4 Steganography
## 1 Introduction  
In contemporary society, the evolution of steganography is intricately linked to the advancements in information technology. Consequently, the emergence of novel forms of interpersonal communication, such as chat, video, and audio, gives rise to innovative data \"carriers\" and, consequently, modern steganographic techniques. Steganography's core principle is to discreetly convey information, ensuring that external observers remain oblivious to the information's presence and the establishment of covert communication. This sets steganography apart from cryptography, which aims to safeguard transmitted content from unauthorized access, potentially revealing the act of communication itself. This term is often confused with other solutions, such as watermarking [1, 2] and cryptography [3] (Figure 1). Nevertheless, it is crucial to distinguish steganography from these other approaches. Cryptography primarily focuses on safeguarding the content of messages, ensuring the confidentiality and integrity of their meaning. On the other hand, watermarking is dedicated to establishing information identity, thereby deterring unauthorized usage. Figure 1: Relationship between cryptography, steganography, and watermarking [4]. Steganographic methods have been recognized and employed for centuries. The term \"steganography\" originates from Greek and translates to hidden writing. The earliest steganographic techniques can be traced back to the fifth century BCE. [PERSON] documented the transmission of information regarding planned attacks on Greece, describing the concealment of messages within the abdominal cavities of hunted animals or through tattooing messages on the heads of trusted slaves, sending these covert messages once their hair regrows. Other known steganographic techniques used over the centuries include using sympathetic ink and micro-dots, placing hidden information in sheet music or plain text, and then reading such hidden data using an appropriate template on the text [5]. Over time, with the rapid evolution of computer technology, a wide range of techniques for hiding data have been introduced into steganography. Remarkably, steganographic techniques have found favor with images [5], allowing data to be discretivelly included in an image's pixel structure without compromising the image's perceived quality. Audio [6] has also emerged as a significant information carrier in steganography. Many ways to conceal data, including an audio signal's frequency and amplitude components, have been tested. This medium adds another degree of camouflage because some frequencies cannot be heard by the human auditory system [6]. Moreover, steganography in videos [7] has been made possible by developing computational powers and its extensive data capacity. This medium allows for covertly embedding information within visual content and extends the potential for concealing data within the audio components. Additionally, the recent rapid advancement of artificial intelligence development has increased its popularity because new techniques are often more accurate than conventional steganography techniques and allow overcoming limitations, e.g., compression and robustness [8]. Another approach is coverless steganography, which achieves covert communication without modifying the carrier itself. Instead of embedding data directly, coverless steganography relies on mapping the concealed information and the carrier medium, whether an image, video, or audio [9; 10; 11]. Beyond multimedia, steganography has extended its reach to internet protocols [12], offering solutions to various network security issues. By embedding information within data packets transmitted over the network and manipulating bits within these packets or their payloads, steganography enables covert data transmission across the internet without raising suspicion. This technique addresses data exfiltration, covert communication, and unauthorized access detection within network security frameworks.