Australians were urged to ignore scam text messages that used death threats to frighten them to give the sender money, credit card details and personal information.
The Australian Communications and Media Authority said it received complaints about the messages from overseas.
They included text such as: "I am about to kill you. If you want to live, contact [email@example.com] to get information on what you will have to do to live. If you ignore this message, you will die!"
Under no circumstances should recipients of the messages reply, disclose personal information or pay money, warned ACMA chairman Chris Chapman.
"Undoubtedly, a member of the public may be distressed to receive such a message but they should not be alarmed," Chapman said.
"These threats are a particularly nasty type of scam. The messages should simply be ignored. [And] if you receive messages of this type, report them to the [authority]."