If you have had an email that warns you about an unlikely-sounding new virus, offers you a free mobile phone, or asks you to update your bank account details, you have received a hoax email. Hoax mail can interrupt work, overload mail systems, or even trick you into giving personal credentials and passwords to criminals.

Virus hoaxes are reports of non-existent viruses. Usually they are emails which do some or all of the following:

Warn you that there is an undetectable, highly destructive new virus.

Ask you to avoid reading emails with a particular subject line, e.g. Join the Crew or Budweiser Frogs.

Claim that the warning was issued by a major software company, internet provider or government agency, e.g. IBM, Microsoft, AOL or the FCC.

Claim that a new virus can do something improbable, e.g. The A moment of silence hoax says that 'no program needs to be exchanged for a new computer to be infected'.

Use techno-babble to describe virus effects, e.g. Good Times says that the virus can put the PC's processor into 'an nth-complexity infinite binary loop'.

Urge you to forward the warning.

On April 1st, 2000 an email headed Rush-Killer virus alert began circulating. It warned of viruses that dialled 911 (the US emergency number), and urged you to forward the warning. The email had the hallmarks of a hoax, but the virus was real.

---

Hoaxes can be as disruptive and costly as a genuine virus.

If users do forward a hoax warning to all their friends and colleagues, there can be a deluge of email. This can overload mail servers and make them crash. The effect is the same as that of the real Sobig virus, but the hoaxer hasn't even had to write any computer code.

It isn't just the end-users who overreact. Companies who receive hoaxes often take drastic action, such as closing down a mail server or shutting down their network. This cripple communications more effectively than many real viruses, preventing access to email that may be really important.

False warnings also distract from efforts to deal with real virus threats.

Hoaxes can be remarkably persistent too. Since hoaxes aren't viruses, your anti-virus software can't detect or disable them.

A hoax can inspire a real virus threat, or vice versa. After the Good Times hoax made headlines, some virus writers waited until it had been debunked and then wrote a real virus with the same name. Some anti-virus firms call this a GT-Spoof.