A corporate investigator can use techniques to identify anonymous users online. Most insiders are still failing to hide their IP address even within their “anonymous” email. Even a fake Gmail account used on the insider’s company network will show the company IP address that your IT department can legally pinpoint to the user. The key is to be creative and get the insider to show you a glimpse of who they are, Gregg says. Gregg is a corporate investigations investigations investigations expert and author of “I Know Who You Are””]
Source: https://www.csoonline.com/article/2124171/tools-to-identify-anonymous-users-online.html