Detecting Attacks and Threats in Elastic Cloud Infrastructures: the Case of Sidechannel Attacks Cloud computing adoption is rising fast. Flexibility, pay-per-use and available resources ondemand with the promise of lower ownership costs are a very attractive value proposition. Virtualization is just a part of Cloud Computing, which leverages virtualization in order to provide resources in an on-demand and pay-per-use fashion. According to the official NIST definition, Cloud Computing can be classified into three main models: • IaaS (Infrastructure as a Service): users have access to on-demand virtual machines and storage which are provided from large shared data centers; • PaaS (Platform as a Service): what is offered by IaaS plus ready-to-use development environment; • SaaS (Software as a Service): on-demand software hosted on a remote server. In this article we will focus on the main security concerns arising in IaaS environment, in particular multitenancy.