The e-mail, if opened, will dial an emergency number, make calls to a "large number" of people or crash the consumer's cell phone, NTT said in a statement posted on its Web site. Although all DoCoMo Internet-ready handsets are susceptible, so far there have been no reports of damage, the company said.
DoCoMo said subscribers of its popular I-mode wireless Net service should be wary of opening e-mails from anyone they don't know or if their phones begin dialing telephone numbers without any prompting. Pushing the "Stop" or "Clear" buttons should end the problem. Removing, then replacing, the phone's battery will unfreeze the phone if it should crash, according to DoCoMo.
Security experts say the DoCoMo warning is another sign that hackers are turning their attentions to wireless devices. An increasing number of phones can download software, which is one way of introducing a virus. Yet, there is no real antivirus protection on the market for phones, making them relatively easy prey.
Mobile phones are only expected to become more sophisticated and simultaneously more prone to attack, security experts say. Java, a software language that lets phones download software, is expected to be installed on more than 100 million phones by the end of 2003.
"Anytime you have mobile code, you are going to have problems," said Richard Smith, chief technology officer from The Privacy Foundation.
Others in the wireless industry agree. In March, Santa Clara, Calif.-based Network Associates, a security software maker, called viruses an "emerging security threat" to mobile devices. Cupertino, Calif.-based Symantec, a security competitor, has heralded handheld computers as "increasingly at risk" and plans to release its own protection for Palms later this month.
Viruses and malicious e-mails also are becoming a way of life for wireless consumers.
In September, researchers at two antivirus companies discovered the first virus, called Phage 1.0, that infects programs on Palm devices.
Last June, Timofonica, a variant of the LoveLetter virus, spammed thousands of mobile phone owners in Spain by routing e-mails through an Internet-to-cellular gateway.