Cyberwarfare
According to Onder (2021), economic sanctions are also information gathering mechanisms for the sanctioning states about the capabilities of the sanctioned states.
In March 2017, WikiLeaks published more than 8,000 documents on the CIA. The confidential documents, codenamed Vault 7 and dated from 2013 to 2016, include details on CIA's software capabilities, such as the ability to compromise cars, smart TVs, web browsers (including Google Chrome, Microsoft Edge, Mozilla Firefox, and Opera Software ASA), and the operating systems of most smartphones (including Apple's iOS and Google's Android), as well as other operating systems such as Microsoft Windows, macOS, and Linux.
In June 2019, the New York Times reported that American hackers from the United States Cyber Command planted malware potentially capable of disrupting the Russian electrical grid.
The United States topped the world in terms of cyberwarfare intent and capability, according to Harvard University's Belfer Center Cyber 2022 Power Index, above China, Russia, the United Kingdom and Australia.
In June 2023, the National Security Agency and Apple were accused by the Russian Federal Security Service (FSB) of compromising thousands of iPhones, including those of diplomats from China, Israel, NATO members, and Syria. Kaspersky Lab said many of its senior staff and managers were also hit by the ongoing attack, which it first suspected in early 2023. The oldest traces of infiltration date back to 2019. Kaspersky Lab said it had not shared the findings with Russian authorities until the FSB announcement.

Cyber mercenary: A cyber mercenary is a non-state actor that carries out cyber attacks for Nation states for hire. State actors can use the cyber mercenaries as a front to try and distance themselves from the attack with plausible deniability.

Cyberpeace: The rise of cyber as a warfighting domain has led to efforts to determine how cyberspace can be used to foster peace.  For example, the German civil rights panel FIfF runs a campaign for cyberpeace − for the control of cyberweapons and surveillance technology and against the militarization of cyberspace and the development and stockpiling of offensive exploits and malware. Measures for cyberpeace include policymakers developing new rules and norms for warfare, individuals and organizations building new tools and secure infrastructures, promoting open source, the establishment of cyber security centers, auditing of critical infrastructure cybersecurity, obligations to disclose vulnerabilities, disarmament, defensive security strategies, decentralization, education and widely applying relevant tools and infrastructures, encryption and other cyberdefenses.
The topics of cyber peacekeeping and cyber peacemaking have also been studied by researchers, as a way to restore and strengthen peace in the aftermath of both cyber and traditional warfare.

Cyber counterintelligence: Cyber counter-intelligence are measures to identify, penetrate, or neutralize foreign operations that use cyber means as the primary tradecraft methodology, as well as foreign intelligence service collection efforts that use traditional methods to gauge cyber capabilities and intentions.

On 7 April 2009, The Pentagon announced they spent more than $100 million in the last six months responding to and repairing damage from cyber attacks and other computer network problems.
On 1 April 2009, U.S. lawmakers pushed for the appointment of a White House cyber security "czar" to dramatically escalate U.S. defenses against cyber attacks, crafting proposals that would empower the government to set and enforce security standards for private industry for the first time.
On 9 February 2009, the White House announced that it will conduct a review of the country's cyber security to ensure that the Federal government of the United States cyber security initiatives are appropriately integrated, resourced and coordinated with the United States Congress and the private sector.
In the wake of the 2007 cyberwar waged against Estonia, NATO established the Cooperative Cyber Defence Centre of Excellence (CCD CoE) in Tallinn, Estonia, in order to enhance the organization's cyber defence capability. The center was formally established on 14 May 2008, and it received full accreditation by NATO and attained the status of International Military Organization on 28 October 2008. Since Estonia has led international efforts to fight cybercrime, the United States Federal Bureau of Investigation says it will permanently base a computer crime expert in Estonia in 2009 to help fight international threats against computer systems.
In 2015, the Department of Defense released an updated cyber strategy memorandum detailing the present and future tactics deployed in the service of defense against cyberwarfare.  In this memorandum, three cybermissions are laid out.  The first cybermission seeks to arm and maintain existing capabilities in the area of cyberspace, the second cybermission focuses on prevention of cyberwarfare, and the third cybermission includes strategies for retaliation and preemption (as distinguished from prevention).
One of the hardest issues in cyber counterintelligence is the problem of cyber attribution. Unlike conventional warfare, figuring out who is behind an attack can be very difficult.

Doubts about existence: In October 2011 the Journal of Strategic Studies, a leading journal in that field, published an article by Thomas Rid, "Cyber War Will Not Take Place" which argued that all politically motivated cyber attacks are merely sophisticated versions of sabotage, espionage, or subversion – and that it is unlikely that cyber war will occur in the future.

Legal perspective: NIST, a cybersecurity framework, was published in 2014 in the US.
The Tallinn Manual, published in 2013, is an academic, non-binding study on how international law, in particular the jus ad bellum and international humanitarian law, apply to cyber conflicts and cyber warfare. It was written at the invitation of the Tallinn-based NATO Cooperative Cyber Defence Centre of Excellence by an international group of approximately twenty experts between 2009 and 2012.
The Shanghai Cooperation Organisation (members of which include China and Russia) defines cyberwar to include dissemination of information "harmful to the spiritual, moral and cultural spheres of other states". In September 2011, these countries proposed to the UN Secretary General a document called "International code of conduct for information security".
In contrast, the United approach focuses on physical and economic damage and injury, putting political concerns under freedom of speech. This difference of opinion has led to reluctance in the West to pursue global cyber arms control agreements. However, American General Keith B. Alexander did endorse talks with Russia over a proposal to limit military attacks in cyberspace. In June 2013, Barack Obama and Vladimir Putin agreed to install a secure Cyberwar-Hotline providing "a direct secure voice communications line between the US cybersecurity coordinator and the Russian deputy secretary of the security council, should there be a need to directly manage a crisis situation arising from an ICT security incident" (White House quote).
A Ukrainian international law scholar, Alexander Merezhko, has developed a project called the International Convention on Prohibition of Cyberwar in Internet. According to this project, cyberwar is defined as the use of Internet and related technological means by one state against the political, economic, technological and information sovereignty and independence of another state. Professor Merezhko's project suggests that the Internet ought to remain free from warfare tactics and be treated as an international landmark. He states that the Internet (cyberspace) is a "common heritage of mankind".
On the February 2017 RSA Conference Microsoft president Brad Smith suggested global rules – a "Digital Geneva Convention" – for cyber attacks that "ban the nation-state hacking of all the civilian aspects of our economic and political infrastructures". He also stated that an independent organization could investigate and publicly disclose evidence that attributes nation-state attacks to specific countries. Furthermore, he said that the technology sector should collectively and neutrally work together to protect Internet users and pledge to remain neutral in conflict and not aid governments in offensive activity and to adopt a coordinated disclosure process for software and hardware vulnerabilities. A fact-binding body has also been proposed to regulate cyber operations.

In popular culture: 

In films: Independence Day (1996)
Terminator 3: Rise of the Machines (2003)
Live Free or Die Hard (2007)
Terminator Genisys (2015)
Snowden (2016)
Terminator: Dark Fate (2019)
Documentaries

Hacking the Infrastructure: Cyber Warfare (2016) by Viceland
Cyber War Threat (2015)
Darknet, Hacker, Cyberwar (2017)
Zero Days (2016)
The Perfect Weapon (2020)

In television: "Cancelled", an episode of the animated sitcom South Park
Series 2 of COBRA, a British thriller series, revolves around a sustained campaign of cyberwar against the United Kingdom and the British government's response to it.

See also: 

References: 

Further reading: Andress, Jason. Winterfeld, Steve. (2011). Cyber Warfare: Techniques, Tactics and Tools for Security Practitioners. Syngress.  ISBN 1-59749-637-5
Bodmer, Kilger, Carpenter, & Jones (2012). Reverse Deception: Organized Cyber Threat Counter-Exploitation. New York: McGraw-Hill Osborne Media. ISBN 0071772499, "ISBN 978-0071772495"
Brenner, S. (2009). Cyber Threats: The Emerging Fault Lines of the Nation State. Oxford University Press. ISBN 0-19-538501-2
Carr, Jeffrey. (2010). Inside Cyber Warfare: Mapping the Cyber Underworld. O'Reilly. ISBN 978-0-596-80215-8
Conti, Gregory. Raymond, David. (2017).