How Precise is the Information
Myths and Reality
You can usually get the precise information about the domain owner, as the owner's contact details are required to register a domain name. There are, of course, exceptions to this rule, because a domain may be registered using a stolen credit card and/or the owner may give fake personal information, although law in many jurisdictions prohibits this practice.
Unlike domains, IP addresses are not individualized to that extent. Usually, when you query an IP address, you get the details of the organization that owns a certain range of IP addresses. This is usually an ISP or company. Therefore, you can find out which ISP the person is using or which company he/she works for, but you can't get the name or address of the specific person who is connected to the Internet using the given IP address. The degree of precision may differ, though. An IP address may belong to a small company or ISP that owns as few as 16 IP addresses. If that's the case, you're in luck: You can find out exactly where the person is located, up to the city district. But if you come across a huge ISP, such as AOL in the United States, all you can get is the location of the main office, and you wouldn't be able to even find out the state or province of the user, although there are other techniques that may help (e.g. the time zone or host name that often reveals the location). These are extreme examples; usually, the degree of precision is rather high.
That said, "I can get someone's address and phone number by IP his/her address" is a myth in most of the cases, at least if we consider an average "investigator." Naturally, a government agency may be capable of tracing the user by contacting the ISP and checking the connection log files. Another popular myth tells of a possibility to always find the sender's IP address in the e-mail headers. Well, that's not always the case, because it's not extremely difficult to hide one's IP address by using a proxy server (an HTTP proxy server in case of web-based e-mail services or SOCKS proxy server in case of the standard POP/SMTP e-mail clients). Again, a government agency may still trace the user.
It's interesting to look at the situation from the standpoint of the user whose IP address is being queried or otherwise analyzed. Is it safe to reveal it? Do you need to hide it? The answer is not an easy one, and it's outside the scope of this tutorial. In brief, if you are looking for anonymity, you should consider implementing some measures to hide it. If you're not particularly concerned about anonymity or privacy, there are still situations where hiding your IP address might be advisable. Consider a news group posting that you made today using an alias, and another one that you made a month ago, under your real name. If you have a static IP address, searching news groups for your IP address will show all your postings, no matter what name you used. This is just one of many possible scenarios.
Anyway, back to SmartWhois ...