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This paper uses multisines and a vector network analyzer (VNA) to achieve a dense-spectral-grid Nonlinear-VNA (NVNA) testbed, so that the inter-modulation nonlinearity of a RF power amplifier can be well characterized in the frequency domain. The multisine signals are provided by vector signal generators, and are used as both the NVNA phase reference and the modulated test stimulus. Based on these frequency-domain measurement results, the nonlinear behavior of the power amplifier under test can be analyzed in frequency, time and envelope domains.

Based on ideal model, and considering the early time effects, the theoretical uncertainty of RMS delay spread simulated by reverberation chamber has been theoretically investigated. The ideal model also shows a new basic understanding for the principle of these RMS delay spread simulations. And uncertainty results could guide the simulation experiments, and make it clear to know how does RMS delay spread results simulated by RC could be believed in a certain range. Specially, numerical results indicate the only small uncertainty is arising from the fluctuation of quality factor of RC.

Code reuse and code injection attacks have become the popular techniques for advanced persistent threat APT to bypass exploit-mitigation mechanisms deployed in modern operating systems. Meanwhile, complex, benign programs such as Microsoft Office employ many advanced techniques to improve the performance. Code execution patterns generated by these techniques are surprisingly similar to exploits. This makes the practical exploit detection very challenging, especially on the Windows platform. In this paper, we propose a practical exploit early detection system called Xede to comprehensively detect code reuse and code injection attacks. Xede can effectively reduce false positives and false negatives in the exploit detection. We demonstrate the effectiveness of Xede by experimenting with exploit samples and deploying Xede on the Internet. Xede can accurately detect all types of exploits. In particular, it can capture many exploits that cannot be captured by mainstream anti-virus software and detect exploits that fail to compromise the systems due to variations in the system configurations.

Recent maturity of virtualization has enabled its wide adoption in cloud environment. However, legacy security issues still exist in the cloud and are further enlarged. For instance, the execution of untrusted software may cause more harm to system security. Though conventional sandboxes can be used to constrain the destructive program behaviors, they suffer from various deficiencies. In this paper, we propose VCCBox, a practical sandbox that confines untrusted applications in cloud environment. Leveraging the state-of-the-art hardware assisted virtualization technology and novel design, it is able to work effectively and efficiently. VCCBox implements its system call interception and access control policy enforcement inside the hypervisor and create an interface to dynamically load policies. The in-VMM design renders our system hard to bypass and easy to deploy in cloud environment, and dynamic policy loading provides high efficiency. We have implemented a proof-of-concept system based on Xen and the evaluation exhibits that our system achieves the design goal of effectiveness and efficiency.