Share 'How to know someone's IP Address'

In many cases, it's desired to know the IP address of someone in the reconnaissance phase. The first question to ask is what information do I have about this person. In most cases it's possible that you have the email or IM of the target. First let's discuss the methods: Method #0x01 if you have a web server hosted someplace where you can see its logs then it's very easy to send someone a URL...