Broadly speaking, there are two complementary approaches to determining what hosts are on a network—you can sweep the entire network using scanning tools as described in Chapter 10, or you can find sources that will tell you what hosts are available. Both approaches have merit—information sources such as DNS, LDAP directories, WINS, and NetBIOS enable you to quickly determine which hosts play important roles. By sweeping a network, you often find hosts that are hidden or considered unimportant, but you’re also much more likely to be noticed. This chapter focuses on using common network databases to discover the available hosts. Network sweeping techniques are the subject of Chapter 10.