The Zero-Trust Architecture (ZTA) security paradigm deploys comprehensive user- and resource-aware defenses both at the network's perimeter and inside the network. However, deploying a ZTA approach requires specifying and managing a large, network spanning set of fine-grained security policies, which will increase administrators' workloads and increase the chance of errors. This paper presents the design and prototype implementation of the NEUTRON policy framework, which provides an automated end-to-end policy pipeline, specification, management, testing, and deployment. NEUTRON uses a flexible, graph-based approach to specify and share complex, fine-grained network security policies. NEUTRON provides a software structure so that policy patterns may be easily shared between organizations, reducing the burden of creating the policy. Administrators assemble the software for their site, and the NEUTRON policy generator creates the entire network-wide security policy. Treating the security policy like software also allows new approaches to policy verification and policy change impact analysis. Thus we designed the Security Policy Regression Tool (SPRT), which uses our novelRuleset Aggregation Algorithm to perform scalable verification of the network-wide security policy across the network model. Moreover, our graph-based framework allows for efficient computation and visualization of the policy change impact.

The scale of ransomware attacks increases every year, and so does its cost, which has reached billions of dollars. A specific class of ransomware, calledcrypto ransomware, encrypts data of the victims for monetary gain. The encryption models adopted in crypto-ransomware can be very diverse, but, regardless, one of the critical aspects of the encryption process is the method used to generate the encryption key. The analysis of such a method can provide valuable information for understanding ransomware's innermost details and features, critical for building defenses. In this article, we analyze the encryption model and the encryption key generation process of ransomware samples from different families. We discuss the analysis methods and tools we used and the challenges in the analysis of ransomware code. Finally, we present the results of our study and discuss algorithms and functions used in modern crypto-ransomware.

The zero trust principle only allows authorized and authenticated actions in a computer network. A network policy satisfies the least privilege principle by minimizing the network permissions to only those needed by users and applications. However, administrators face many challenges in creating a least privilege policy since it requires a detailed understanding of the network topology and knowing the communication requirements of every network application and user. This paper addresses those challenges by introducing a graph-based policy specification framework to capture a network's communication requirements and a network compiler that turns those requirements into an enforceable policy. To offset the effort of building such a stringent policy, we incorporate patterns to spread the work of policy creation over time and people. In the paper, we first elaborate on how our framework's semantics enhances network security and resilience. We then introduce a Security Policy Regression Testing tool (SPRT), which leverages our framework's semantics, to test and reason about consistency, correctness, and relevance of network security policies. Finally, we outline relevant research directions.

Zigbee network security relies on symmetric cryptography based on a pre-shared secret. In the current Zigbee protocol, the network coordinator creates a network key while establishing a network. The coordinator then shares the network key securely, encrypted under the pre-shared secret, with devices joining the network to ensure the security of future communications among devices through the network key. The pre-shared secret, therefore, needs to be installed in millions or more devices prior to deployment, and thus will be inevitably leaked, enabling attackers to compromise the confidentiality and integrity of the network. To improve the security of Zigbee networks, we propose a new certificate-less Zigbee joining protocol that leverages low-cost public-key primitives. The new protocol has two components. The first is to integrate Elliptic Curve Diffie-Hellman key exchange into the existing association request/response messages, and to use this key both for link-to-link communication and for encryption of the network key to enhance privacy of user devices. The second is to improve the security of the installation code, a new joining method introduced in Zigbee 3.0 for enhanced security, by using public key encryption. We analyze the security of our proposed protocol using the formal verification methods provided by ProVerif, and evaluate the efficiency and effectiveness of our solution with a prototype built with open source software and hardware stack. The new protocol does not introduce extra messages and the overhead is as lows as 3.8% on average for the join procedure.

This paper focuses on checking the correctness and robustness of the AT command interface exposed by the cellular baseband processor through Bluetooth and USB. A device's application processor uses this interface for issuing high-level commands (or, AT commands) to the baseband processor for performing cellular network operations (e.g., placing a phone call). Vulnerabilities in this interface can be leveraged by malicious Bluetooth peripherals to launch pernicious attacks including DoS and privacy attacks. To identify such vulnerabilities, we propose ATFuzzer that uses a grammar-guided evolutionary fuzzing approach which mutates production rules of the AT command grammar instead of concrete AT commands. Empirical evaluation with ATFuzzer on 10 Android smartphones from 6 vendors revealed 4 invalid AT command grammars over Bluetooth and 13 over USB with implications ranging from DoS, downgrade of cellular protocol version (e.g., from 4G to 3G/2G) to severe privacy leaks. The vulnerabilities along with the invalid AT command grammars were responsibly disclosed to affected vendors and two of the reported vulnerabilities have been already assigned CVEs (CVE-2019-16400 and CVE-2019-16401).