located in a non-secured zone [4]. The temperature signal can move around the chip by heat transfer among processor cores until it reaches the destination (receiver) [3; 5]. In such cases, the bit \"1\" shows as a range of rising and is full of the temperature signal, while a bit \"0\" shows no changes. While thermal signals are committed to transferring temperature signals over a chip, it is highly likely to be degraded or disrupted by the environment temperature variations or the thermal noise [5]. An advanced countermeasure against the thermal covert channel needs to position affected cores and fight the TCC attacks. In recent years, some new designs of thermal covert channels have been proposed. For instance, [PERSON] et al. [4] introduced a new design of thermal covert channels that has improved noise immunity and throughput. They showed the feasibility of side channels and especially thermal channels on multi-core systems for the first time, e.g., they created a 1-hop TCC channel (a channel of transmitter and receiver are 1-hop apart from each other) that could reach a throughput of 1.33 bps along with a BER of 11%. In this study, researchers did not consider power consumption and high BER. In separate research [6] it was confirmed that a TCC channel has a throughput of more than 45 bps, and it also showed a TCC channel with a throughput of more than 5 bps with a BER less than 1%. Apparently, the ever-growing performance of the thermal covert channels pose serious risks and dangers to sensitive information or data security in today's many-core/multicore systems [7]. However, it is stated in [3; 5] that TCC can be countered by decreasing the frequency of the system by Dynamic Voltage Frequency Scaling (DVFS) technology, producing jamming noise with the same transmission frequency as TCC [8] or as in [9] by limiting the accessibility to thermal information, etc. The increase in operating temperature of an embedded system results in a bad experience and reliability problems. Reliability issues through system design are being extensively examined. It seems that in today's digital world, TCC attacks are posing an increasingly big security threat to multi-core/many-core systems, however, there have been little works done to improve the defence strategy or countermeasure against them. In this paper, we focus on thermal covert channel attacks and propose a novel selective noise-based countermeasures. We have aimed to consider the weakness of previous works and propose a new countermeasure in a way that is undetectable by the attackers. For instance, [PERSON] et al. [3; 5] introduced a detection based on signal frequency scanning, positioning affected cores, and blocking to thwart possible TCC attacks, as shown in Figure 2. All experiments are performed using a simulator, Sniper-v7.2 [10; 11], and more details of the simulator are provided in Section 5. However, it seems that the temperature signal is still at risk because the attackers can come up with a new method and find the thermal signal's pattern. [PERSON] et al. [12] suggested a countermeasure strategy based on scanning frequency spectrum rapidly to detect any possible attack. When a  
Figure 1: TCC communication in an eight multi-core system. The arrow from core A to core B indicates that the heat flows from core A to core B.  
thermal covert channel is detected and its frequency of transmission is found, a strong noise source is applied to the transmission frequency band for targeted jamming. These examples [3; 5; 12] have motivated us to propose a new countermeasure scheme based on recording temperature and adding extra noise (extra thread), in fact, selective noise, that changes the pattern of the thermal signal. The purpose of adding a selective noise is to generate more temperature when the bit is \"1\", which results in increasing the duration of bit \"1\". For instance, if the bit was \"1\" just for 2 ms, by the proposed method we increased it to 5 ms and modified the behaviour of the temperature signal. The rest of this paper is structured as follows.