An introduction to Socio Technical Security. STS-ml is a Socio-Technical Security modeling language for the specification of security and trustworthiness requirements of systems operating in a cross-organizational environment. The language is built on top of social concepts, such as role, agent, goal, delegation, authorization, etc. STS-Tool is the CASE tool for STS-ml, it is an Eclipse RCP application and supports multi-view modeling. The tutorial presents both the modeling language and the tool. More details visiting http://www.sts-tool.eu.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant no 257930 (ANIKETOS project: http://www.aniketos.eu/).