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Cloud Computing offers on-demand infrastructure, platform and software services over the Internet on a pay-as-you-use model. Many e-commerce businesses and social networking sites are moving towards the cloud. Security breaches have also started to grow along with their popularity. The malicious processes can target virtualization-based cloud infrastructure and harm virtual resources, thereby becoming a threat to the cloud. Several Intrusion Detection Systems (IDSs) have been developed to detect attacks based on predefined behavior patterns. However, malicious processes can hide their behavior in the presence of security mechanisms on a Virtual Machine (VM). With the increasing frequency of such attacks, IDSs must be improved using Machine Learning (ML) and Deep Learning (DL) techniques. This study proposes a novel intrusion detection framework that can detect known and unknown attacks by system call sequence analysis. The framework analyzes the system call sequences of VMs with a hybrid model of Long Short Term Memory (LSTM) and system call frequency-based anomaly detection techniques. The proposed framework is evaluated using the Australian Defence Force Academy-Linux Dataset (ADFA-LD) dataset. Compared to the existing frameworks, the highest accuracy of 97.2% and a false positive rate of 2.4% are achieved for our proposed framework. [ABSTRACT FROM AUTHOR]

The immense popularity of social networks has rendered them vulnerable to security threats such as Sybil attacks. In Sybil attacks, attackers send several friend requests from fake identities, and some of the genuine users might accept them unknowingly and become victims of Sybil attacks. Once genuine users accept friend requests from Sybil identities, attackers can spam, phish, and conduct other harmful actions in the target networks. Though genuine users have links to Sybil users unknowingly, they do less interaction and have low strength of relationship with them. Thus, the relationship strength measure can be useful to detect a Sybil attack. Considering the relationship strength measure, we propose a behavior-based and graph-based hybrid approach to detect a Sybil attack in Online Social Networks (OSNs). We identify the behavior features, use them to measure the relationship strength, and identify attack edges. We use the graph-based feature(betweenness-centrality) to leverage attack-edge identification and detect Sybil nodes. We have evaluated our scheme using real-world datasets, and experimental results validate the proposed scheme's effectiveness. [Display omitted] • A hybrid scheme is suggested to detect Sybil attacks in online social networks. • We identify and apply behavior-based important features to identify attack edges. • An important graph-based structural feature is employed to detect Sybil nodes. • The proposed scheme is effective and outperforms current approaches. [ABSTRACT FROM AUTHOR]