With the threats of cybercrime, cyberterrorism and cyberwarfare looming over our hyper-connected world, the best defense for the U.S. might be a good offense, says new research by a University of Illinois expert in technology and legal issues. Law professor Jay P. Kesan warns that an active self-defense regime, which he terms "mitigative（缓和的） counterstriking," is a necessity in cyberspace, especially to protect critical infrastructure such as banking, utilities and emergency services.

"The threats from cyber-attacks are real, and the harm of a potential attack can be far greater than what we can currently combat," Kesan said.

Kesan's analysis, co-written with former U. of I. law student Carol M. Hayes and published in a forthcoming issue of the Harvard Journal of Law and Technology, concludes that mitigative counterstriking against attacks instead of simply relying on passive defense options (firewalls, patches and anti-virus software) is legally justifiable as self-defense, although a more exhaustive legal framework needs to be implemented.

"The principles of mitigative counterstriking are legally justifiable under several areas of domestic and international law, and can be made consistent with other areas of law by amending or reinterpreting the law," he said.

Kesan says an active defense regime consists of three distinct elements: detecting intrusions, tracing the attack back to the attacker, and executing a counterstrike.

A counterstrike can be characterized in one of two ways: retributive（报应的，惩罚的） counterstrikes, which punish the attacker; and mitigative counterstrikes, which minimize the damage to the victims' information-technology infrastructure.

According to the authors' study, there currently is no effective domestic or international legal apparatus to deter cyber-attacks. Criminal law enforcement is complicated by the lack of a consistently enforced international law, jurisdictional issues and the difficulty of identifying an attacker in a manner specific enough to justify criminal prosecution. Resorting to civil litigation（诉讼，起诉） would likely be slow and impractical.

"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?"

Kesan suggests that a government-affiliated agency, preferably a public-private partnership, should be responsible for an active defense program, including providing resources for private parties to detect and trace intrusions, and executing counterstrikes.