Caller: Claiming to be NBN security checkup

There was a delay before anyone responded to my hello, like you get with a call center. An Indian accent said they believed that they were talking to the main NBN user and then claimed that someone had been illegally using the NBN. When I asked which property they were talking about, they could not answer. They then ask how many users there were, whether any third party had access and whether I had shared the password. ... I hung up.
Clearly a dangerous scam.