The Australian Communications and Media Authority has issued warnings to the general public after it received reports of death threats being made via mobile phone text messages. The bogus SMSes inform people that they are about to be killed if they do not contact an e-mail address and follow instructions.

Australian mobile subscribers were left with a feeling of uneasiness after receiving messages on their phones that read, "I am about to kill you. If you want to live, contact (xxx@xxx.com) to get information on what you will have to do to live. If you ignore this message, you will die!."

The actual number of people who received such death threats is not yet known, but it was apparently big enough to get the Australian Communications and Media Authority (ACMA) to issue an alert about them.

"These threats are a particularly nasty type of scam. The messages should simply be ignored – they are intended to frighten recipients into providing money, credit card details and personal information to the scammer," ACMA Chairman Chris Chapman said.

Preliminary investigation suggests that the messages originate overseas, but it is not clear how attackers obtained the targeted phone numbers. Security experts speculate that the networks of some less secure carriers might have been breached, allowing cybercrooks to steal customer databases.

"Undoubtedly, a member of the public may be distressed to receive such a message, but they should not be alarmed," Mr. Chapman advised, noting that people were encouraged to report SMS spam to ACMA via its specialized website or by calling the dedicated phone line at 1300 855 180.

"Thinking logically I thought to myself it has to be a scam of some sort ... but even so it was upsetting," Judy Adamson, a freelance journalist from Sydney and the target of such a message, commented for The Age. "What about if I'd been a little old lady or if I'd been a 12-year-old girl, or if English wasn't my first language and I didn't understand what to do?," she added.

Such extortion attempts are not something new, but they used to occur mostly over e-mail. Sending death threats via SMS is likely to increase their credibility. People are generally accustomed to the vast amount of daily e-mail spam, but not so much when it comes to their private mobile phone numbers.