It has become extremely difficult to distinguish a benign application from a malicious one as the number of untrusted applications on the Internet increases rapidly every year. In this project, we develop a lightweight application confinement mechanism for Linux systems in order to aid most users to increase their confidence in various applications that they stumble upon and use on a daily basis. Developed sandboxing facility monitors a targeted application’s activity and imposes restrictions on its access to operating system resources during its execution. Using a simple but expressive policy language, users are able to create security policies. During the course of the traced application’s execution, sandboxing facility makes execution decisions according to the security policy specified and terminates the traced application if necessary. In the case of an activity that is not covered by the policy, the facility asks for user input through an user interface with a simple human readable format of the activity and uses that user input to make execution decisions and to improve the security policy. Our ultimate goal is to create a facility such that even casual users with minimal technical knowledge can use the tool without getting overwhelmed by it. We base our tool on system call interposition which has been a popular research area over the past fifteen years. Developed sandboxing facility offers an user-friendly, easy to use user-interface. It monitors the given application and detects activities that might possibly be system intrusions. Moreover, the tool offers logging and auditing mechanisms for post-execution analysis. We present our evaluation of the tool in terms of performance and overhead it generates when confining applications. We conclude that developed system is successful in detecting abnormal application activity according to specified security policies. It has been obtained that the tool adds a significant overhead to the target applications. However, this overhead does not pose usability issues as our target domain is personal use cases with small applications.