The Nine Network has suffered what it describes as the largest cyber attack on a media company in Australia's history, which the federal government says is a lesson for all businesses.
"Whether it's criminal sabotage or the work of a foreign nation is still being investigated, but this attack could reveal a nationwide vulnerability," 9News Australia tweeted.
While Nine called in the nation's cyber detectives, Parliament House pulled the plug on the federal email network at the weekend in response to a suspected cyber attack.
Both incidents are under investigation by the public face of the Australian Signals Directorate, the Australian Cyber Security Centre.
Acting Defence Minister Marise Payne said the lead cyber security agency is very focused on working with businesses to make sure they are protecting themselves.
"This is a salutary reminder that no one is immune," Senator Payne told reporters on Monday.
Parliament's email network was shut down due to a fault that Assistant Defence Minister Andrew Hastie said was linked to an external provider.
The connection to government systems was severed immediately as a precaution.
"The government acted quickly to defend the integrity of the system," Mr Hastie told 3AW on Monday.
"To talk about attribution, we can only do so when it's in the national interest and it's clear, and that's a matter of judgement for the prime Minister and the cabinet."
On Monday evening, the Department of Parliamentary Services said it had "commenced a staged restoration of services on DPS issued smart phones and tablets" after the weekend's disruption.
"Protective mechanisms have operated correctly to prevent an unsophisticated attempt to access the Parliamentary Computer Network," the DPS said in a statement.
"The network was not compromised and there is no identified data loss."
Parliament's outage followed the Nine Network confirming it was the target of a cyber attack over the weekend, which disrupted its live programming out of Sydney.
Western Australia's Parliamentary Services Department was also attacked earlier in March, while many of Melbourne's Eastern Health service systems still remain offline after a "criminal" cyber incident almost two weeks ago.
Shadow treasurer Jim Chalmers said the latest cyber attack on Nine was very concerning.
"What we're hearing about here is a serious, and sophisticated, targeted attack on a media organisation," he told reporters.
The Australian broadcaster was unable to air its Weekend Today and Sunday Sports programs on Sunday morning and later attributed the outage to an attack on its systems.
In a note to staff, Nine's director of people and culture Vanessa Morley directed all employees across the country to work from home until further notice.
"Our IT teams are working around the clock to fully restore our systems which have primarily affected our broadcast and corporate business units," she wrote.
"Publishing and radio systems continue to be operational."
Ms Morley asked office workers to work from home using their own internet network.
Nine's National Rugby League coverage, 6pm news bulletins and Sunday evening coverage went ahead as planned as the company enacted contingency arrangements.
The ACSC is urging organisations using Microsoft Exchange to urgently patch a number of vulnerabilities so they're not exposed to potential compromise.