The good name of the Australian Federal Police was used for a scam email that informed recipients that their credit cards were detected as being used in transactions linked to criminal organisations.
It went on to tell recipients to click a link in the email.
It told recipients not to contact their banks or the local authorities under threat of legal action.
Peter Sykora, AFP national co-ordinator of High Tech Crime Investigations at AFP, said the email was signed by 'Scott Sykes', a federal police officer.
"The AFP became aware of the scam on the night of 1 July and the matter was referred to the AFP High Tech Crime Operations, [the following morning]," he said.
Sykora said the law enforcement organisation doesn't know how many people were affected by the scam.
"Calls have been received from members of the public and international partners."
A copy of the fake email follows:
"Australian Federal Police case no : 24531987/AFP/832
"The AFP's Criminal Justice Information Services (CJIS) Division has been notified about several suspicious payments from your credit card account. Upon closer investigation we concluded that nine (9) of your payments are related to known criminal organizations, some of them currently under investigation for participating in the recent cybernetic attacks on Commonwealth Bank of Australia. Your case has received code 2 priority and you are under suspicion of aiding known criminals. Your credit card account may have helped the criminals in their attacks.
"In order to prove your lack of culpability please click here (this is a secure link to our server).
"Please note that failure to cooperate will lead to the advancement of our investigation. You will be prosecuted to the full extent of the law. Your assets and funds will be frozen until the end of our investigation.
"This is a federal investigation, you will not contact your local authorities or bank; you will wait for one of our agents to contact you within 48 hours. We suspect local involvment in this matter. Failure to do so will ad a charge of "obstruction of justice" to you.
"As a measure of precaution AFP is able to provide free monitoring of your account against all future hacking and phishing attack. We respect your privacy, we will not monitor your account transactions or personal info. Our software has a 99.57 percent rate of success in detecting and stoping cybernetic attacks. Also we have agents supervising the software 24/7. If you wish to subscribe to this service, more info will be provided when our agent contacts you."