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Locating hosts with large connection degree is very important for monitoring anomalous network traffics. The in-degree (out-degree), defined as the number of distinct sources (destinations) that a network host is connected with (connects) during a given time interval. Due to massive amount of data in high speed network traffics and limit on processing capability, it is difficult to accurately locate hosts with large connection degree over high speed links on line. In this paper we present a new data streaming method for locating hosts with large connection degree based on the reversible connection degree sketch to monitor anomalous network traffics. The required memory space is small and constant, and more importantly the update/query complexity would not depend on the amount of data. The hash functions for data sketch are designed based on the remainder characteristics of the number theory so that in-degree/out-degree associated with a given host can be accurately estimated. Although the connection degree sketch does not preserve any host address information, we can analytically reconstruct the host addresses associated with large in-degree/out-degree by a simply equation purely based on the characteristics of the hash functions without using any host address information. This procedure is highly efficient since the computational time is constant and ignorable. Furthermore, this reversible connection degree sketch based method can be easily implemented in distributed systems. The experimental and testing results based on the actual network traffics show that the new method is truly accurate and efficient.

System security monitoring has become more and more difficult with the ever-growing complexity and dynamicity of the Internet of Things (IoT). In this paper, we develop an Intelligent Maintenance and Lightweight Anomaly Detection System (IMLADS) for efficient security management of the IoT. Firstly, unlike the traditional system use static agents, we employ the mobile agent to perform data collection and analysis, which can automatically transfer to other nodes according to the pre-set monitoring task. The mobility is handled by the mobile agent running platform, which is irrelevant with the node or its operation system. Combined with this technology, we can greatly reduce the number of agents running in the system while increasing the system stability and scalability. Secondly, we design different methods for node level and system level security monitoring. For the node level security monitoring, we develop a lightweight data collection and analysis method which only occupy little local computing resources. For the system level security monitoring, we proposed a parameter calculation method based on sketch, whose computational complexity is constant and irrelevant with the system scale. Finally, we design agents to perform suitable response policies for system maintenance and abnormal behavior control based on the anomaly mining results. The experimental results based on the platform constructed show that the proposed method has lower computational complexity and higher detection accuracy. For the node level monitoring, the time complexity is reduced by 50% with high detection accuracy. For the system level monitoring, the time complexity is about 1 s for parameter calculation in a middle scale IoT network.

The decentralised nature of blockchain technologies can well match the needs of integrity and provenances of evidences collecting in digital forensics across jurisdictional borders. In this work, a novel blockchain based digital forensics investigation framework in the Internet of Things (IoT) and social systems environment is proposed, which can provide proof of existence and privacy preservation for evidence items examination. To implement such features, we present a block enabled forensics framework for IoT, namely IoT forensic chain (IoTFC), which can offer forensic investigation with good authenticity, immutability, traceability, resilience, and distributed trust between evidential entitles as well as examiners. The IoTFC can deliver a gurantee of traceability and track provenance of evidence items. Details of evidence identification, preservation, analysis, and presentation will be recorded in chains of block. The IoTFC can increase trust of both evidence items and examiners by providing transparency of the audit train. The use case demonstrated the effectiveness of proposed method.

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