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Alysson Bessani

Publications and source records attributed to Alysson Bessani.

23 records · Page 2Linked to original sources

Cyberthreat Detection from Twitter using Deep Neural Networks

To be prepared against cyberattacks, most organizations resort to security information and event management systems to monitor their infrastructures. These systems depend on the timeliness and relevance of the latest updates, patches and threats provided by cyberthreat intelligence feeds. Open source intelligence platforms, namely social media networks such as Twitter, are capable of aggregating a vast amount of cybersecurity-related sources. To process such information streams, we require scalable and efficient tools capable of identifying and summarizing relevant information for specified assets. This paper presents the processing pipeline of a novel tool that uses deep neural networks to process cybersecurity information received from Twitter. A convolutional neural network identifies tweets containing security-related information relevant to assets in an IT infrastructure. Then, a bidirectional long short-term memory network extracts named entities from these tweets to form a security alert or to fill an indicator of compromise. The proposed pipeline achieves an average 94% true positive rate and 91% true negative rate for the classification task and an average F1-score of 92% for the named entity recognition task, across three case study infrastructures.

cs.LG↗

SITAN: Services for Fault-Tolerant Ad Hoc Networks with Unknown Participants

The evolution of mobile devices with various capabilities (e.g., smartphones and tablets), together with their ability to collaborate in impromptu ad hoc networks, opens new opportunities for the design of innovative distributed applications. The development of these applications needs to address several difficulties, such as the unreliability of the network, the imprecise set of participants, or the presence of malicious nodes. In this paper we describe a middleware, called SITAN, that offers a number of communication, group membership and coordination services specially conceived for these settings. These services are implemented by a stack of Byzantine fault-tolerant protocols, enabling applications that are built on top of them to operate correctly despite the uncertainty of the environment. The protocol stack was implemented in Android and NS-3, which allowed the experimentation in representative scenarios. Overall, the results show that the protocols are able to finish their execution within a small time window, which is acceptable for various kinds of applications.

cs.DC↗

A Byzantine Fault-Tolerant Ordering Service for the Hyperledger Fabric Blockchain Platform

Hyperledger Fabric (HLF) is a flexible permissioned blockchain platform designed for business applications beyond the basic digital coin addressed by Bitcoin and other existing networks. A key property of HLF is its extensibility, and in particular the support for multiple ordering services for building the blockchain. Nonetheless, the version 1.0 was launched in early 2017 without an implementation of a Byzantine fault-tolerant (BFT) ordering service. To overcome this limitation, we designed, implemented, and evaluated a BFT ordering service for HLF on top of the BFT-SMaRt state machine replication/consensus library, implementing also optimizations for wide-area deployment. Our results show that HLF with our ordering service can achieve up to ten thousand transactions per second and write a transaction irrevocably in the blockchain in half a second, even with peers spread in different continents.

cs.CR↗

Efficient and Modular Consensus-Free Reconfiguration for Fault-Tolerant Storage

Quorum systems are useful tools for implementing consistent and available storage in the presence of failures. These systems usually comprise a static set of servers that provide a fault-tolerant read/write register accessed by a set of clients. We consider a dynamic variant of these systems and propose FreeStore, a set of fault-tolerant protocols that emulates a register in dynamic asynchronous systems in which processes are able to join/leave the servers set during the execution. These protocols use a new abstraction called view generators, that captures the agreement requirements of reconfiguration and can be implemented in different system models with different properties. Particularly interesting, we present a reconfiguration protocol that is modular, efficient, consensus-free and loosely coupled with read/write protocols, improving the overall system performance.

cs.DC↗

SMaRtLight: A Practical Fault-Tolerant SDN Controller

The increase in the number of SDN-based deployments in production networks is triggering the need to consider fault-tolerant designs of controller architectures. Commercial SDN controller solutions incorporate fault tolerance, but there has been little discussion in the SDN literature on the design of such systems and the tradeoffs involved. To fill this gap, we present a by-construction design of a fault-tolerant controller, and materialize it by proposing and formalizing a practical architecture for small to medium-sized scale networks. A central component of our particular design is a replicated shared database that stores all network state. Contrary to the more common primary-backup approaches, the proposed design guarantees a smooth transition in case of failures and avoids the need of an additional coordination service. Our preliminary results show that the performance of our solution fulfills the demands of the target networks. We hope this paper to be a first step in what we consider a necessary discussion on how to build robust SDNs.

cs.NI↗