An extensive crypto-ransomware attack has targeted Australia Post customers and has also affected the ABC's TV studios.

The hacking attack, which reportedly originated in Russia, uses fake emails containing a link which downloads malicious software.

Computer users are being warned not to open any email attachments they receive.

Australia Post has warned its customers about fake emails which advise that a "courier" has been unable to deliver a parcel to their address.

The email then requests the customer to open attachments which provide information about their package and asks them to go to their local post office to collect the package.

Australia Post stressed to all customers that if they received such an email it should be deleted immediately.

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"Australia Post takes the safety and security of our customers extremely seriously," the company said in a statement.

"Australia Post has received notification from the Australian Communications and Media Authority of new phishing sites originating from Russia using Australia Post branding.

"We are promptly actioning takedowns of these sites to protect customers."

An image obtained on October 7, 2014, from Symantec's website, showing a computer screenshot after a ransomware attack. ( Symantec )

The ABC said an "IT security issue" affected ABC News 24 programming for half an hour on Tuesday morning.

"There was an IT security issue this morning which affected some of the ABC's broadcasting systems and created technical difficulties for ABC News 24," it said in a statement.

Sorry, this video has expired Crypto-ransomware attack targets Australian businesses ( Jake Sturmer )

"As a result, we broadcast stand-by programming from 9:30am before resuming live news broadcasts from Melbourne at 10:00am.

"We are now operating normally."

Telstra's Queensland media manager Matthew Martyn-Jones said while staff emails were targeted several weeks ago, they have not been affected by the latest scam.

"It's not uncommon for phishing emails to appear from time to time," he said.

"These scams are designed by criminals who want to target staff for one reason or another.

"It's a timely reminder to people to stop and think before clicking anything that looks suspicious."

What is crypto-ransomware?

Crypto-ransomware is a relatively new and increasingly pervasive type of ransomware that aims to collect personal and financial information or install a malicious virus which can "take over" your PC.

Recovery of infected systems is virtually impossible without clean backups.

Ransomware is a type of software, or malware, used to extort money from victims by preventing access to their computer or files.

The Federal Government's Stay Smart Online website suggests the following as the best prevention ways to avoid ransomware and other malware attacks: