Responding to cyberattacks traced back to state actors is one of the most delicate challenges in international relations.

The goal is to deter future attacks and impose costs without inadvertently escalating to open conflict, especially in a domain where attribution is difficult, effects can be ambiguous, and traditional deterrence theories don't always apply.

Here's a layered approach countries can take, moving from less escalatory to more assertive responses:

I. Defensive and Resilience-Building Measures (Primary, Continuous Response):

This is the foundational and least escalatory response, crucial for minimizing harm and demonstrating resilience.

1. Strengthen Cybersecurity Defenses:

   • Patching and Vulnerability Management: Immediately identify and patch exploited vulnerabilities (as seen after the Hafnium attacks).

   • Enhanced Detection & Response: Improve capabilities to detect intrusions quickly, contain them, and eradicate the adversary from networks.

   • Network Segmentation & Zero Trust: Implement architectural changes to limit lateral movement and ensure strict access controls.

   • Secure Backups and Recovery: Ensure robust, isolated backups to enable rapid recovery from destructive attacks.

   • Supply Chain Security: Address vulnerabilities in the digital supply chain, vetting third-party software and hardware.

2. Information Sharing & Collaboration:

   • Domestic Coordination: Foster strong collaboration between government agencies, critical infrastructure operators, and the private sector to share threat intelligence and best practices.

   • International Alliances: Leverage existing alliances (NATO, QUAD, ASEAN, Five Eyes) to share threat intelligence, coordinate defenses, and develop common standards.

3. Public Awareness & Education: Educate citizens and businesses about common tactics (e.g., phishing) used by state-sponsored actors to make them less susceptible to initial compromise.

II. Diplomatic and Economic Responses (Non-Kinetic, Coercive):

These responses aim to impose costs and signal displeasure without direct military action.

1. Public Attribution ("Naming and Shaming"):

   • Objective: Impose reputational costs on the aggressor state, signal attribution capabilities, set international norms, and rally allies.

   • Execution: A government (or coalition of governments) formally and publicly attributes the attack to a specific state actor, often providing technical details or intelligence assessments. (e.g., U.S. and allies attributing Hafnium to China).

   • Considerations: Requires high confidence in attribution, may lead to diplomatic friction, and might reveal intelligence sources.

2. Diplomatic Demarches & Protests:

   • Objective: Formally express displeasure and warn the aggressor that their actions are unacceptable.

   • Execution: Summoning the ambassador, issuing a formal diplomatic note, or making official statements through foreign ministries. Can be private or public.

3. Sanctions:

   • Objective: Impose economic costs on the aggressor state or specific entities/individuals involved in the cyberattack.

   • Execution: Targeted sanctions against individuals (e.g., indicted hackers), specific state-owned entities, or broader sectoral sanctions (e.g., restrictions on technology exports). (e.g., U.S. sanctions against Russian GRU officers or North Korean entities).

   • Considerations: Effectiveness varies, can have unintended economic consequences, and may require international coordination.

4. Legal Action (Indictments):

   • Objective: Deny safe haven to individual perpetrators, demonstrate commitment to the rule of law, and raise the personal risk for cyber operators.

   • Execution: Issuing indictments against identified hackers, often leading to international arrest warrants. (e.g., U.S. indictments against Chinese APT41 members or North Korean Lazarus Group members).

   • Considerations: Requires strong evidence, relies on international cooperation for arrests, and often symbolic if perpetrators remain in their home country.

5. Expulsion of Diplomats:

   • Objective: A strong diplomatic signal of displeasure, often used in conjunction with other measures.

   • Execution: Expelling diplomats suspected of intelligence activities or as a general protest against hostile actions.

6. Withdrawal from or Suspension of Agreements:

   • Objective: Pressure the aggressor by withdrawing from bilateral agreements or suspending cooperation in certain areas.

   • Execution: This is a more significant step that can have broader implications for relations.

III. Cyber Countermeasures (Proportional Response in Cyberspace):

These involve offensive cyber actions taken in response, but are carefully calibrated to avoid escalation.

1. "Hacking Back" / Reciprocal Cyber Operations:

   • Objective: Disrupt the aggressor's ongoing cyber operations, degrade their capabilities, or impose costs by targeting their infrastructure or data.

   • Execution: This can range from defacing websites to taking down C2 servers, disrupting their internal networks, or exfiltrating data (e.g., to expose their activities).

   • Considerations:

     • Proportionality: The response must be proportionate to the original attack (e.g., if data was stolen, perhaps exfiltrating similar data from the aggressor).

     • Necessity: The response must be necessary to stop the attack or deter future ones.

     • Reversibility: Ideally, countermeasures should be reversible and avoid permanent damage.

     • Attribution Clarity: Requires very high confidence in attribution to avoid hitting the wrong target.

     • Escalation Risk: This is the most sensitive area, as a miscalculated or misinterpreted countermeasure can easily escalate the conflict.

2. Defensive Counter-Cyber Operations (DCC/Active Defense):

   • Objective: Directly disrupt ongoing attacks or remove an adversary's presence from networks.

   • Execution: This might involve infiltrating the attacker's infrastructure (e.g., their C2 servers) to delete malware, disrupt their operations, or gather further intelligence on their TTPs.

   • Considerations: Often conducted under a nation's existing defensive mandate but can still carry risks if operations extend beyond a purely defensive posture.

IV. Legal Framework and Escalation Control:

• International Law: States generally agree that existing international law, including the UN Charter, applies to cyberspace. The key challenge is interpreting concepts like "use of force" and "armed attack" in the cyber context. Responses must adhere to principles of necessity and proportionality.

• Thresholds: Most cyber espionage or minor disruptions do not cross the threshold of an "armed attack" that would justify a kinetic military response. Only cyberattacks with effects comparable to a conventional armed attack (e.g., causing death, injury, or significant physical destruction) might justify self-defense under Article 51 of the UN Charter.

• De-escalation Mechanisms: Maintaining back-channel communications and clear signaling of intent are vital to prevent miscalculation and unintended escalation. The ambiguity of cyber operations makes this particularly challenging.

By adopting a diverse toolkit of responses, carefully calibrated to the nature and severity of the attack, countries can aim to deter malicious state actors, protect national interests, and reinforce international norms without inadvertently triggering wider, open conflict. Taiwan, being a frequent target, must continuously refine its multi-layered defense and deterrence strategies, leveraging international partnerships while navigating complex geopolitical realities.