In intelligence organizations, agent handling is the management of so-called agents (called secret agents or spies in common parlance), principal agents, and agent networks (called "assets") by intelligence officers typically known as case officers. Human intelligence A primary purpose of intelligence organizations is to penetrate a target with a human agent, or a network of human agents. Such agents can either infiltrate the target, or be recruited "in place". Case officers are professionally trained employees of intelligence organizations that manage human agents and human agent networks. Intelligence that derives from such human sources is known by the abbreviation HUMINT. Sometimes, agent handling is done indirectly, through "principal agents" that serve as proxies for case officers. It is not uncommon, for example, for a case officer to manage a number of principal agents, who in turn handle agent networks, which are preferably organized in a cellular fashion. In such a case, the principal agent can serve as a "cut-out" for the case officer, buffering him or her from direct contact with the agent network. Using a principal agent as a cut-out, and ensuring that the human agent network is organized in a cellular fashion, can provide some protection for other agents in the network, as well as for the principal agent, and for the case officer if an agent in the network is compromised. Assuming that standard principles of intelligence tradecraft have been strictly observed by the principal agent and the agents in the network, compromised agents will not be able to identify the case officer, nor the other members of the network. Ideally, agents may work side by side in the same office, and conduct their clandestine collection activities with such discipline, that they will not realize that they are both engaged in espionage, much less members of the same network. Since an agent can sometimes identify his or her principal agent, however, or reveal information under interrogation that can lead to the identification of a principal agent, the protection provided by cellular network organization can be time-sensitive. If principles of intelligence tradecraft have not been strictly observed, it is also possible that compromised agents can reveal information that exposes other members of the network. In the real world of espionage, human lapses are very much the norm, and violations of the principles of tradecraft are common. It is for this reason that agents are ideally trained to resist interrogation