The agency's director-general Mike Burgess appeared before a Senate estimates committee on Tuesday afternoon to warn of the foreign interference threat to politicians and Australia's national intelligence community.

"Almost every sector of Australian society is a potential target of foreign interference," Mr Burgess said.

"The level of foreign interference is high at all levels of government, it's actually higher at local than state and federal."

In response to the potential threat, Mr Burgess said ASIO would be providing federal politicians with information on how to deal with it.

"In the coming weeks, I will write to all Commonwealth Parliamentarians to warn they are attractive targets for those trying to steal our secrets and manipulate our decision making," Mr Burgess said.

The letters, Mr Burgess said, would contain "high level advice on what to look for and how they should handle it".

Senator Kristina Keneally questioned whether letters were enough given the level of threat Mr Burgess suggested existed to parliamentarians.

"ASIO and myself, we don't turn our mind to the training of this - the policy response to the nature of the threat," Mr Burgess said.

"This is an attempt to draw this particular threat to the attention of members of parliament."

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Mr Burgess also later repeated an example outlined in the agency's annual report of a foiled espionage attempt by an undisclosed foreign state.

The plot involved an Australian-based foreign national and a team of foreign intelligence officers who ASIO alleged were trying to recruit Australians with security clearances.

"The agents wanted sensitive information about their intelligence activities, particularly those directed against their home country," Mr Burgess said.

The investigation into the plot took a "couple of years" and was finally disrupted with no sensitive information being lost to the foreign intelligence service.

When asked what would have happened had intelligence been lost to the plot, Mr Burgess responded the agency's capabilities would be damaged.

"If they were lost to us that [would] mean that country would know what we might be doing that meets our own national interest," Mr Burgess said.

"It may even include, particularly because they were after intelligence activities against their country, what we might know about them, and obviously that would damage our capabilities."

Mr Burgess would not provide any further details on operational matters.