(CNN) -- A dog tapping away at a computer keyboard turns to another dog and says, "On the Internet, nobody knows you're a dog." The cartoon by Peter Steiner, which first appeared in The New Yorker in July 1993, perfectly encapsulates the world we live in today. How do you trust someone to be who they say they are on the Internet? The question has bubbled up again after news broke that Notre Dame linebacker Manti Te'o fell for a "catfish," someone who fakes an identity online to finagle his or her way into a fraudulent romantic relationship. We do our best to avoid being duped. But it's not always easy.
@highlight
Notre Dame Linebacker Manit Te'o falls for a 'catfish'
@highlight
A 1993 iconic cartoon lampoons Internet identity foibles
@highlight
In an official account, even President Obama posted a pic to positively ID himself
@highlight
After Nigerian banking frauds came phishing, SMShing, vishing
Online identity scams have multiplied in form and name, phishing via e-mail spread to text messages, prompting the term "@placeholder."