Low Level Security in Java

The Java(tm) language allows Java-compatible Web browsers to download code fragments dynamically and then to execute those code fragments locally. However, users must be wary of executing any code that comes from untrusted sources or that passes through an insecure network. This paper presents the details of the lowest-levels of the Java security mechanism. Before any downloaded code is executed, it is scanned and verified to ensure that it conforms to the specifications of the virtual machine