Washington, June 28 (IANS) A proactive defence -- detecting intrusions, tracing the attacker and executing a counterstrike -- can act as a powerful deterrent against cyber-terrorism and cyber-warfare that threaten our hyper-connected world.

It is vitally necessary to protect critical infrastructure like banking, utilities and emergency services from such attacks, warns law professor Jay P. Kesan at the University of Illinois.

"The threats from cyber-attacks are real, and the harm of a potential attack can be far greater than what we can currently combat," the Harvard Journal of Law and Technology quoted Kesan as saying.

Kesan, who co-wrote his analysis with former Illinois law student Carol M. Hayes, concludes that such "mitigative counterstrikes" against attacks, instead of simply relying on passive defence options (firewalls, patches and anti-virus software), are legally justifiable as self-defence.

Kesan says an active defence regime comprises three distinct elements: detecting intrusions, tracing the attack back to the source, and executing a counterstrike, according to an Illinois statement.

A counterstrike can be characterised in one of two ways: retributive counterstrikes which punish the attacker, and mitigative counterstrikes which minimise the damage to the victims' information-technology infrastructure.

"Cyber-attacks are fundamentally different from crime," Kesan said.

"The person may be physically very far away from you, and you may not be able to use traditional legal remedies against that person, since civil and criminal remedies require jurisdiction over a person. In those circumstances, what do you do?" he asked.