In 1996, Sony Corp. had to break its no-comment policy on acquisition rumors when a fake e-mail purportedly from its chairman to Apple Computer's CEO started making the rounds.
What they did was mail letters to 10 fake addresses in 159 countries and see how long it took them to be returned, and what percentage of them are returned.
The US Computer Emergency Readiness Team (US-CERT) has told computer users to be wary of potential e-mail scams, as well as fake anti-virus and phishing attacks regarding the Japan earthquake and the tsunami disasters.