Nathanael Paul
University of Virginia
USA

David Evans
University of Virginia
USA

Many systems execute untrusted programs in virtual machines (VMs) to limit their access to system resources. Sun introduced the Java VM in 1995, primarily intended as a lightweight platform for execution of untrusted code inside web pages. More recently, Microsoft developed the .NET platform with similar goals. Both platforms share many design and implementation properties, but there are key differences between Java and .NET that have an impact on their security. This paper examines how .NET's design avoids vulnerabilities and limitations discovered in Java and discusses lessons learned (and missed) from Java's experience with security in enforcing low-level code safety, defining policies, associating particular policies with running code, and enforcing security policies on executions.

Keywords: Java, .NET, virtual machine security

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