SQL Server Email - vulnerability issues and prevention strategies

One of the optional features available to users of the Microsoft SQL Server(R) database is the ability to send and receive Email messages programmatically from the database. Email is often an ideal way to send administrative alerts to system staff and/or end users when unusual conditions are detected, to distribute various kinds of routine reports, etc. Many modern databases share this ability to send Email, and SQL Server Email capabilities have been available at least as early as version 6.0. The SQL Server implementation is somewhat unique among relational databases, however, in its ability to accept and process incoming as well as outgoing messages. This aspect of the Email feature in SQL Server - the ability to send a message to the database and have it automatically execute a query and reply to the sender - presents a potential vulnerability that could easily be overlooked. This paper will explore some of the ways this feature could be used by both legitimate users and intruders. Installation and configuration of the utility will be briefly described in enough detail to support the ensuing discussion of the vulnerability. Finally, a number of strategies will be suggested that could be used to minimize the vulnerabilities exposed by use of this feature.