Online impersonations: no validation required
How do you know what's real and what's not?
It's fun playing hide-and-seek with my four-year-old niece. She will shout from behind the curtains, "I'm over here!" Unfortunately, most online imposters will not tell you where they are hiding, or even when they are going to start. You have to find them and you must constantly be looking. If you maintain a low profile online - never posting to forums and not maintaining a public image - then you might only need to look around once every few months. However, if you are more widely known, then consider looking more often, such as weekly or even every few days.
The first step in the search process is to perform an ego-search. Start with search engines such as Google, Alta Vista, and Yahoo!. Perform searches for yourself. Look for your name, company, anything that you are well-known for, and anything you recently did publicly that may have been noteworthy. Use a variety of different search engines since different tools return different results (While Google may have the largest index, other search engines find things that Google misses.)
Strictly searching for web pages will only return web pages. However, impersonators may use a variety of forums. Consider tools such as Google Groups to search newsgroups and MARC to scan technical mailing lists.
Technorati is an excellent place for searching blogs - particularly since Google does not index MySpace pages.
There are two main things to look for during your ego-search. First, look for things posted by you. Make sure they are things that you actually posted. Second, look for things attributed to you. Even if you don't initially find an impersonator, you will probably find references to an impersonator.
Rather than doing the searches yourself, companies such as Reputation Defender and Naymz have been established to help manage your online profile. For a fee, these companies will identify potentially damaging online information about you - whether it was created by you or by an imposter (however, I have no direct experience with either of these services).
Hopefully you won't find an impersonator. However, if you do then the next step is to mitigate damage. The mitigation process depends on the type and degree of impersonation.
You have mail?
Configuring a mailer to send email as someone else is beyond trivial. When you configure your Microsoft Outlook mailer (or Gnome Evolution or Firefox Thunderbird or Eudora, etc.), you simply need to enter in a fake email address. While laws such as the US CAN-SPAM act makes email impersonation illegal, who is going to catch you? Fortunately, uni-directional emails can usually be identified as forgeries fairly quickly. Any kind of return correspondence will not reach the imposter.
Unfortunately, free mail and web service, such as Yahoo! Mail and Google's Gmail, make it trivial to create "similar enough" addresses that can fool many people. As a recipient, you should check the sender's email address to make sure it really is from the person you expected. Do not assume that the sender is using a new email address unless they told you about it ahead of time.