A top security expert has warned cyber criminals will be targeting Australia during the G20 Leaders Summit in Brisbane next week, with people and non-government agencies likely to be the "weakest link".

Tobias Feakin, director of the International Cyber Policy Centre in Canberra, said organisations and individuals that did not have extensive security measures as extensive as those of their government counterparts could provide a back door for hackers to gain top secret information.

Police and security staff undertake a G20 preparation exercise. Cyberspace is also getting a security treatment. Credit:Glenn Hunt

"In the past we have seen, in certain attacks, a pattern where the attacker looks for the weakest link into the most confidential information," Mr Feakin told Fairfax Media.

The best such example was the so-called "Titan Rain" series of attacks on the Pentagon and other US agencies during the mid 2000s, in which Chinese hackers gained access to the IT networks of defence subcontractors, which provided a "rich source of information", Mr Feakin said.