Two of the nation's most senior security officials have made a rare public appearance to spell out exactly what internet data they want kept under controversial new data retention plans.

It comes as ASIO warns that despite the terror threat remaining at "medium" its agency is in “overload” because of the increased number of potential terror attacks around the country.

"The terrorist threat is suddenly starting to impact on Australian citizens to a greater degree than it has in the past": David Irvine. Credit:Alex Ellinghausen

And the country’s top spy has indicated he would be willing to accept more oversight when it comes to accessing metadata, including requiring authorities to secure a “generic warrant” that is currently not required.

Cabinet has approved plans to introduce mandatory data retention but uncertain explanations from Prime Minister Tony Abbott and Attorney-General George Brandis this week have fuelled confusion over exactly what sort of metadata the telcos would be required to store and whether it would include a user's web browsing history.