Modern cloud-based applications are composed of several microservices that interact over a network. They are complex distributed systems, to the point that developers may not even be aware of how microservices connect to each other and to the Internet. As a consequence, the security of these applications can be greatly compromised. This work explicitly targets this context by providing a methodology to assess microservice connectivity, a software tool that implements it, and findings from analyzing real cloud applications. Specifically, it introduces Kubesonde, a cloud-native software that instruments live applications running on a Kubernetes cluster to analyze microservice connectivity, with minimal impact on performance. An assessment of microservices in 200 popular cloud applications with Kubesonde revealed significant issues in terms of network isolation: more than 60% of them had discrepancies between their declared and actual connectivity, and none restricted outbound connections towards the Internet. Our analysis shows that Kubesonde offers valuable insights on the connectivity between microservices, beyond what is possible with existing tools.