In the last 10 years we have witnessed a strong integration of several human activities with computers and digital networks. This has led to an interconnected economy, where interactions occur through the mediation of networked devices. The openness of this scenario was instrumental in creating new business opportunities. However, it has also paved the way to new forms of criminal activities that, while happening in the cyber domain, have strong implications in the real world. The current trend towards an Internet of Things will possibly worsen this scenario. In this context, private companies and public bodies struggle to defend their businesses against a deluge of attacks spanning from complex online frauds to malicious scanning activities of their IT infrastructures. As attacks continue to grow in complexity, classic "border-control" approaches to system security quickly prove to be ineffective, calling for an investigation into new methodologies and solutions. At the same time, ongoing research efforts on "Big Data" systems are devising new and innovative methodologies to manage and analyze large amounts of data with the aim of recognizing specific patterns and behaviors. The First International Workshop on Big Data Analytics for Security aims to bring together people from both academia and industry to present their most recent work related to trust, security and privacy issues in big data analytics, together with application of big data technologies in the field of security. The purpose is to establish if and how large-scale data analytics technologies can help in creating new security solutions for today's complex IT infrastructures.