Masking one's IP address is a standard practice when conducting illicit activities. A well-configured proxy provides robust anonymity and does not log activity, thereby frustrating law enforcement efforts to identify the original location of the person(s) involved. A proxy allows actors to send network traffic through another computer, which satisfies requests and returns the result. Students or employees can use proxies to communicate with blocked services such as Internet Relay Chat (IRC) and instant messaging, or to browse websites that administrators block. Attackers also use proxies because Internet Protocol (IP) addresses are traceable, and they do not want to reveal their true locations. As one example, iDefense wrote about the fast-flux architecture (ID# 484463), which uses a proxy infrastructure to satisfy requests. Proxies are also a common source of spam e-mail messages, which use open relays (a simple mail transfer protocol [SMTP] proxy). In a distributed database system, a program often referred to as the database's "back end" runs constantly on a server, interpreting data files on the server as a standard relational database. Programs on client computers allow users to manipulate that data, using tables, columns, rows, and fields. To do this, client programs send SQL statements to the server. The server then processes these statements and returns replies to the client program.