Cyber attackers demand ransom: police

Computer systems are being held to ransom through malicious cyber criminals, police warn.

South Australia's electronic crime unit has received multiple reports of malicious software being used to infect systems until ransom demands are met.

In one style of attack, user files are encrypted through an email attachment.

Where users have backups of files, data can be recovered. But not all are so lucky.

"For those who do not have backups, recovery at this stage is not possible and all data will be lost unless payment is made to the criminal entities," police say.

Cyber attacks through compromised websites have also been reported.

Deleting emails with attachments from unknown people and ensuring website security is up to date can help prevent attacks, police say.