|Fig. 1: U.S. Strategic Nuclear Forces from 1991 to 2016. (Source: J. Park, after Woolf. )|
United States has the largest stockpile of nuclear warheads in the world. The immense destructive power, however, also meant that the nation could face great danger if the nuclear arsenal security system were breached.
Cyber espionage attempts have existed for as long as nuclear arsenals have. Israeli secret service's attack on a Syrian government official's computer, dubbed 2007 Operation Orchard, used a Trojan horse program to steal information. The Iranian nuclear network was attacked by a malware known as Stuxnet in 2010, utilizing utilized at least 5 undiscovered vulnerabilities of the system.  In 2008 Operation Buckshot Yankee, nothing more than an infected USB drive was used to breach the air-gapped United States classified networks.  Even more alarming, 2007 Aurora Generator test demonstrated that cyber attacks can even cause physical destruction by triggering nuclear explosions. 
The inherent difficulty of maintaining digital security is that additional security measures introduce complexity to the system. As Professor Martin Libicki of the Pardee RAND Graduate School explains, "complexity is bad for security. It creates more places for bugs to lurk, makes interactions among software components harder to understand, and increases flow rate of packets well past where anyone can easily reconstruct what happened when things go wrong". 
The most potent weapon known to humankind should be treated with extreme care in secure systems. This report examines efforts being made to protect the United States nuclear arsenal from potential threats.
United States recognizes nuclear surety as an overriding national priority. It has implemented multiple measures to enhance the security of missiles equipped with nuclear warheads. Of them, the three recent measures that stand out are de-MIRVing, open-ocean targeting, and component isolation. de-Mirving process was finished in June 2014. It involved reconfiguration of intercontinental ballistic missiles (ICBMs) to make each missle carry only one nuclear warhead.  Open-ocean targeting is setting the default target of ICBMs and submarine-launched ballistic missiles (SLBMs) to open ocean, so that an unsolicited launch, whether it be accidental or intentional cyber attack, will lead to the missile landing in open ocean.  Lastly, component isolation is physically detaching components essential to detonation to prevent unintended explosions from cyber espionage or environmental factors such as lightning and power surge.
International collaboration and reduction of nuclear weapons are strengthening the rigor of United States nuclear arsenal security and decreasing the number of potential targets of attacks. Security breach to a nation's nuclear arsenal can harm more than just one nation. Based on that understanding, 35 nations pledged to join a new initiative to jointly strengthen their nuclear security implementation at the 2014 Nuclear Security Summit.  As the Stanley Foundation explains, United States has also been working with Russia and China to review and enhance each other's nuclear arsenal network securities.  In particular, best practice exchanges with Russia proved useful in exploring insider protection, vulnerability assessment, design basis threat methodology, and performance testing.  Furthermore, United States is also increasing transparency and reducing all nuclear weapons as promised under Nuclear Nonproliferation Treaty. In fact, in 2014, United States was holding only 10% of the non-strategic nuclear weapons that it held in September of 1991. As Fig. 1 shows, the U.S. nuclear weapons stockpile has been in steady decline. As of 2016, the total stockpile of nuclear weapons was under one fourth of the stockpile in 1991.
Increasing security can be achieved by reducing vulnerabilities. Each reduced warhead is one less target for adversaries.
© Junwon Park. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 A. Futter, "Cyber Threats and Nuclear Weapons," Royal United Services Institute for Defense and Security Studies, July 2016.
 "Report of the United States of America Pursuant to Actions 5, 20, 21 of the 2010 Nuclear Non-Proliferation Treaty Review Conference Final Document," U.S. Department of State, 27 Apr 15.
 "Strengthening International Nuclear Security Cooperation ," Stanley Foundation, 15 Oct 14.
 A. F. Woolf, "U.S. Strategic Nuclear Forces: Backgroud, Developments, and Issues," Congressional Research Service, RL33640, February 2017.