As critical information systems are increasingly moved from mainframe and proprietary platforms to open system environments, the management and implementation of security faces complex challenges. This article describes several of the security challenges raised by heterogeneous, distributed database environments; for example, distributed authentication services, encryption of network data and secure remote database administration. It then proposes how some of these challenges can be addressed by using current and forthcoming releases of Oracle server and networking products. It also briefly discusses the increased complexity of those challenges in a multilevel secure environment. This article focuses primarily on aspects of security which concern confidentiality (or privacy) of information rather than those which concern integrity (or correct maintenance of information) and availability (or proper accessibility to information and continuity of that service). However, measures which protect confidentiality, such as password control, often also help to protect against threats to integrity and availability.