A networks can take hours if not days to complete. Unlike the traditional Ping Sweep utilities, that waits for a response from each system before moving on to the next host. If the initial target attempt and non-intrusive probing haven't turned up any immediate results. The attacker will turn to identifying valid user accounts, or poorly protected resource shares. There are many ways to extract valid account or exported resource names from a system by using a process called enumeration.
Enumeration involves active connections to a system and directed queries.
As such, they must be logged on or otherwise noticed. Much of the information collected through enumeration may appear to be harmless. Once a valid username or share is enumerated, it's usually only a matter of time before the hacker guesses the corresponding password or identifies some weakness associated with the resource sharing protocol. There are also commercial products such as CyberCop scanner, and Internet Security scanners may be used. These are for sale on the open market.