Mobile agent technology is a new research field. The purpose of this report is to take a closer look of this new field, identify its problems, and describe its current state. The theoretical section of this report defines the three properties of agents: mobility, executability and autonomy. The security implications of these properties are analyzed, and some suggestions for protection techniques are given. A hostile mobile agent can act like a virus, infecting the computer and doing serious damage. Many mobile agent systems have been developed in recent years but several of them have been discontinued, because of security issues and an immature research field. This report also suggests that the mobile agents can be seen as a promising new paradigm for distributed programming of future computer networks.