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James Martin/CNET

April 13. Mark it down in your calendars -- it's "National Get a VPN Day."

Privacy advocate group Digital Rights Watch is calling on all Australians to hide the trail they leave behind online, as Australia's mandatory data retention scheme comes into effect.

In March 2015, Parliament passed laws requiring all ISPs and telcos to store telecommunications metadata on their customers. The government gave telcos until April 12 this year to implement their metadata collection schemes under those obligations. And that date is here.

"It's important that we mark this date -- and pause to remember that a detailed picture of the private lives of Australian citizens is being collected by telecommunication companies on behalf of the government," said Chair of Digital Rights Watch Tim Singleton Norton.

"That's why we've declared [April 13] as a national day of action -- we're calling upon Australian citizens to educate themselves about the scale of this surveillance and take precautions accordingly."

If you're wondering whether to get Attorney-General George Brandis a card for National Get a VPN Day, don't bother. He'll already know what's inside the envelope before he opens it.