Traditionally, network security has been based on the principle of segmentation, dividing the network into different segments or perimeters to secure resources. The security of computer systems based on network segmentation has a drawback as attacks can propagate within sub-networks. To mitigate this risk, Zero Trust (ZT) concept, giving no trust for any entity by default, has been adopted to evaluate the trust level of each communication flow based on the knowledge it has about user information, network security policies and Threat Intelligence sources. To detect cyberattacks and secure resources, Cyber Threat Intelligence (CTI) is essential. It identifies potential threats to a computer system. This research aims to formalize the trust in each piece of CTI information gathered in order to make decisions in cybersecurity.