We present a general unwinding framework for the definition of information flow security properties of concurrent programs, described in a simple imperative language enriched with parallelism and atomic statement constructors. We study different classes of programs obtained by instantiating the general framework and we prove that they entail the noninterference principle. Accurate proof techniques for the verification of such properties are defined by exploiting the Tarski decidability result for first-order formulae over the reals. Moreover, we illustrate how the unwinding framework can be instantiated in order to deal with intentional information release and we extend our verification techniques to the analysis of security properties of programs admitting downgrading. © IOS Press and the authors. All rights reserved.