Many popular programs, such as Netscape, use untrusted helper applications to process data from the network. Unfortunately, the unauthenticated network data they interpret could well have been created by an adversary, and the helper applications are usually too complex to be bug-free. This raises significant security concerns. Therefore, it is desirable to create a secure environment to contain untrusted helper applications. We propose to reduce therisk of a security breachby restricting the program's access to the operating system. In particular, we intercept and filter dangerous system calls via the Solaris process tracing facility. This enabled us to build a simple, clean, user-mode implementation of as ecure environment for untrusted helper applications. Our implementation has negligible performance impact, and can protect pre-existing applications.

While interactive multimedia animation is a very compelling medium, few people are able to express themselves in it. There are too many low-level details that have to do not with the desired content---e.g., shapes, appearance and behavior---but rather how to get a computer to present the content. For instance, behaviors like motion and growth are generally gradual, continuous phenomena. Moreover, many such behaviors go on simultaneously. Computers, on the other hand, cannot directly accommodate either of these basic properties, because they do their work in discrete steps rather than continuously, and they only do one thing at a time. Graphics programmers have to spend much of their effort bridging the gap between what an animation is and how to present it on a computer.