Security

FSI scholars produce research aimed at creating a safer world and examing the consequences of security policies on institutions and society. They look at longstanding issues including nuclear nonproliferation and the conflicts between countries like North and South Korea. But their research also examines new and emerging areas that transcend traditional borders – the drug war in Mexico and expanding terrorism networks. FSI researchers look at the changing methods of warfare with a focus on biosecurity and nuclear risk. They tackle cybersecurity with an eye toward privacy concerns and explore the implications of new actors like hackers.

Along with the changing face of conflict, terrorism and crime, FSI researchers study food security. They tackle the global problems of hunger, poverty and environmental degradation by generating knowledge and policy-relevant solutions. 

-

The Hoover Project on China’s Global Sharp Power and the Stanford Center for International Security and Cooperation 
invite you to

Danger Zone: The Coming Conflict with China

Featuring

Hal Brands

Hal Brands

Distinguished Professor of Global Affairs, Johns Hopkins School of Advanced International Studies (SAIS)
Michael Beckley

Michael Beckley

Associate Professor of Political Science, Tufts University
Larry Diamond

Larry Diamond

Senior Fellow, Hoover Institution
Glenn Tiffert

Glenn Tiffert

Research Fellow, Hoover Institution

About the Speakers

Hal Brands is the Henry A. Kissinger Distinguished Professor of Global Affairs at the Johns Hopkins School of Advanced International Studies (SAIS) and a senior fellow at the American Enterprise Institute. He writes a weekly column for Bloomberg Opinion on foreign policy and is the author or editor of several books, including his newest books, The Twilight Struggle: What the Cold War Teaches Us About Great-Power Rivalry Today, and Danger Zone: The Coming Conflict with China, with Michael Beckley. He is a member of the State Department’s Foreign Affairs Policy Board and previously worked as a special assistant to the secretary of defense.

Michael Beckley is an associate professor of political science at Tufts University and a nonresident senior fellow at the American Enterprise Institute. He is a leading expert on the balance of power between the United States and China, and the author of two books and multiple award-winning articles. Previously, Professor Beckley was an International Security Fellow at Harvard's Kennedy School of Government and worked for the U.S. Department of Defense, the RAND Corporation, and the Carnegie Endowment for International Peace. He continues to advise offices within the U.S. intelligence community and U.S. Department of Defense.

Larry Diamond is a senior fellow at the Hoover Institution, ​Mosbacher Senior Fellow in Global Democracy at the Freeman Spogli Institute for International Studies (FSI), and a Bass University Fellow in Undergraduate Education at Stanford University. He co-chairs the Hoover Institution’s programs on China’s Global Sharp Power and on Taiwan in the Indo-Pacific Region.

Glenn Tiffert is a research fellow at the Hoover Institution and a historian of modern China. He co-chairs the Hoover project on China’s Global Sharp Power and works closely with government and civil society partners to document and build resilience against authoritarian interference with democratic institutions. Most recently, he co-authored and edited Global Engagement: Rethinking Risk in the Research Enterprise (2020).

Hybrid

Hal Brands Johns Hopkins School of Advanced International Studies
Michael Beckley Tufts University
Larry Diamond (Host) Hoover Institution
Glenn Tiffert (Discussant) Hoover Institution
Seminars
-

Register to Attend

About the Event: How do perceptions of international affairs vary between countries? To what extent do technology companies mediate these perceptions? International relations scholarship has largely neglected the role of internet search engines, yet they are a ubiquitous method by which people seek information about the world. This study conducts a large-scale audit of Google Search Engine Result Pages (SERPs) for various topics related to international affairs. Our preliminary results indicate three patterns. First, variation in localized results strongly correlates with user language, suggesting that language is a primary factor mediating people’s exposure to information about international affairs. Second, we find significant differences in the reach of ideological content, including state propaganda as well as material from transnational advocacy networks. Finally, we trace how SERPs change in response to salient events. Analyzing results related to the 2022 Ukraine crisis generated both before and after the Russian invasion, we find that geographic clustering in the content of SERPs becomes more substantial following the invasion, suggesting an increase in localization. Substantively, this analysis contributes to several literatures, including the role of technology in international politics, surveillance capitalism, and AI governance. Methodologically, this paper is the first in the field (to our knowledge) to use SBERT, a state-of-the-art natural language processing model for sentence embeddings.

About the Speaker: Rochelle Terman is an Assistant Professor of Political Science at the University of Chicago. She received her Ph.D. in Political Science with a designated emphasis in Gender & Women’s Studies from the University of California, Berkeley. Before coming to Chicago, she was a Postdoctoral Fellow at the Center for International Security and Cooperation at Stanford University. Her research interests focus on international norms, human rights, and computational social science.

 All CISAC events are scheduled using the Pacific Time Zone.

William J. Perry Conference Room

Rochelle Terman University of Chicago
Seminars
News Feed Image
headshot_rochelle_terman.jpeg
Authors
News Type
News
Date
Paragraphs

Steven C. Házy Lecturer, Rose Gottemoeller, testified today before the Senate Armed Services Committee (SASC) in Washington D.C., on the United States' nuclear strategy and policy. While testifying, Gottemoeller emphasized the following three points:

  1. New START constraints continue to serve U.S. national interests as we modernize our arsenal. If unchecked, Russia could dramatically expand its missel and warhead arsenal.
  2. We must focus on the race in emerging technologies, considering China's deep investments in that area, but be ready to respond if they rush a nuclear buildup.
  3. Arm's control is in the U.S. interest, and engaging both Russia and China in the sphere will be necessary.

 

Read the full opening statement below.

Hero Image
Rose Gottemoeller
All News button
1
Subtitle

Rose Gottemoeller's main takeaways from her opening statement while testifying before the SASC

Authors
News Type
Commentary
Date
Paragraphs

Ukraine's army has recently recaptured a lot of territory from Russia. They also have analysts asking a question, not for the first time, what happens if Russian President Vladimir Putin feels cornered? NPR's Michele Kelemen reports. Listen below for Steven C. Házy Lecturer's, Rose Gottemoeller's comments on the ongoing war between Ukraine and Russia.

Hero Image
Vladimir Putin and Volodymyr Zelenskyy
Russian President Vladimir Putin (left) and Ukrainian President Volodymyr Zelenskyy (right) | photo credit: TASS News Agency_WikiCommons and REUTERS/Jonathan Ernst
All News button
1
Subtitle

Ukraine's battlefield victories are a reason for celebration. But could it could also usher in another dangerous phase — with Russia's President Vladimir Putin lashing out in other ways.

Authors
Steven Pifer
News Type
Commentary
Date
Paragraphs

On Vladimir Putin’s order, the Russian army launched a new invasion of Ukraine in February.  That has inflicted tragedy on Ukrainians but, seven months later, has also proved a catastrophe for Russia.  By all appearances, Putin remains fixed on his war of choice, now betting the West’s will to support Ukraine will ebb with time.  The West should ensure that that becomes another one of his grievous miscalculations.

A War Gone Awry

On February 24, Russian forces attacked Ukraine from the north, east and south.  The assault vectors suggested they sought to occupy Kyiv and as much as the eastern two-thirds of Ukraine.  Staunch resistance drove the Russians back from the capital.  By early April, Russian forces had withdrawn from Kyiv and the north, though they occupied parts of southern Ukraine.  Moscow then proclaimed the downsized goal of taking Donbas, consisting of the Luhansk and Donetsk oblasts, parts of which Russian and Russian proxy forces had occupied since 2014.

After more than three months of grinding fighting, the Russian army held most of Luhansk oblast.  In July, the Russians turned their military efforts to Donetsk oblast but made scant progress.  Western experts begin speaking of the Russian army’s “culmination”—the point where the combination of casualties (particularly of experienced personnel), loss of equipment, troop exhaustion and low morale make it difficult for a force to sustain a coherent offensive.

After six months of fighting, the conflict seemed to have become a war of attrition.  However, the Ukrainians launched a counteroffensive in Kherson, aimed at driving Russian forces from the only area west of the Dnipro River that they occupied.  They then struck in the Kharkiv region, routing Russian forces and liberating more than 2000 square miles in the first two weeks of September.  While the Russian military continues to occupy large swathes of Ukraine, the tide of war has shifted in Kyiv’s favor, as poor leadership, tactics and logistics hamper Russian forces.

Growing Losses for Russia

The war has meant heavy losses for Russia, first and foremost in its military ranks.  In mid-August, Western intelligence estimated that 15,000-25,000 Russian soldiers had been killed in action and another 45,000-60,000 wounded (the Russians have not reported casualty numbers since March).  These totals have certainly grown over the past month.  The Russian military has also lost substantial amounts of equipment, including confirmed losses of 1100 tanks, 1200 infantry fighting vehicles and thousands of other items.  The Russian defense budget will require many years to replace that equipment, and the Russian army increasingly must make do with older weapons, such as T-62 tanks first produced five decades ago.  Russian arms exporters will likely find that the Russian brand has lost much of its luster with overseas customers.

Western sanctions are exacting a growing economic price.  While the Central Bank of Russia has managed the crisis well, inflation still ran at a hefty 14 percent in September.  In August, the Central Bank reported that the Russian economy had contracted by 4 percent since 2021.  A confidential study purportedly done for the Kremlin provided a grim outlook, projecting an “inertial” scenario of the economy’s contraction bottoming out in 2023 at 8.3 percent below its 2021 level.  The European Union’s coming embargo on most imports of Russian oil and the G7’s planned price cap could significantly cut the revenues that Moscow earns from oil exports.

The West’s ban on export of semiconductors and other high tech products affects both Russia’s defense and civilian manufacturing sectors, and the impact will grow with time.  Since the beginning of the war, more than 1000 multinational companies have exited Russia altogether or substantially curtailed operations there.  There is also brain drain, with tens of thousands of IT specialists reported to have left the country.

Russia has also incurred steep geopolitical costs.  NATO is reenergized, and almost all members are increasing their defense spending.  Putin and the Kremlin did not like the small multinational battlegroups that NATO deployed as trip-wire forces in the Baltic states in 2015; they will like even less the scaled-up contingents being deployed there now.  And the entry of Finland and Sweden into the Alliance will make the Baltic Sea, in effect, a NATO lake.

In sum, Putin’s war has cost Russia much.

Disaster and Dilemma

A series of miscalculations led Putin to this disaster.  The Kremlin apparently did not believe the Ukrainians would resist and expected a quick victory.  Some invading Russian units crossed the border with only two-three days of food rations.  The Kremlin overestimated the might of its military.  Anecdotal reports, such as one that T-80 tank reactive armor was filled with rubber instead of an explosive charge, suggest that corruption, endemic in Russia, has not left the defense sector untouched.  The Kremlin also apparently did not expect NATO’s sharp response, the decisions by Finland and Sweden to seek to join the Alliance, the Western flow of arms to Kyiv, or the scale of economic sanctions.

Russia itself is not yet in crisis.  The economy, while grappling with growing problems, has not broken down, and the Russian military retains formidable capabilities.  But the Kremlin faces a far more difficult situation than it imagined in January, and it will get worse.

Whether Putin fully grasps this is an open question.  On September 7, he said that “we [Russia] have not lost anything and will not lose anything,” a bizarre assessment that the many thousands of Russian families who have lost loved ones in Ukraine surely do not share.  Russian officials have indicated that Kremlin conditions for ending the war remain unchanged from the total capitulation they demanded at the start.  Following a September 13 phone call with Putin, German Chancellor Olaf Scholz noted “there was no indication that new attitudes are emerging.”

Putin faces limits in continuing the war, some self-imposed.  He termed the invasion a “special military operation” (calling it a “war” in Russia can lead to jail time), and he has sought to minimize the scale of the conflict in the eyes of the Russian public.  Despite heavy casualties, the Kremlin officials say they are “not discussing” mobilization.  Russia instead has scrapped the age limit for contract soldiers while scouring prisons for volunteers.  Calls outside the Kremlin have increased for a major mobilization.  However, that could alarm the broader Russian public, who will fear their sons will be drafted and sent to fight.  In any case, it would take considerable time to train new units and equip them with modern arms.

Putin’s Big Bet

The Ukrainian military may well rack up further gains before winter, when the pace of fighting should slow, but the war will continue for some time.  The question:  will the growing economic pain and agonizing flow of dead and injured soldiers home erode the Russian will to fight, or will a weak economy and lack of weapons and ammunition erode Ukraine’s ability to defend itself?

The West has a say in this.  If it continues to provide the arms and financial support the Ukrainians need, their military has the resolve to prevail and defeat the Russian invasion.  Putin is betting, however, that Western support will falter.  He hopes the rising price of energy and costs of assisting Ukraine will undermine European and U.S. support for Kyiv.

The West must stay the course and show Putin his bet is a loser.

Hero Image
President of Russia Vladimir Putin
All News button
1
Subtitle

On Vladimir Putin’s order, the Russian army launched a new invasion of Ukraine in February. That has inflicted tragedy on Ukrainians but, seven months later, has also proved a catastrophe for Russia.

0
Senior Research Scholar, FSI
Visiting Fellow in Israel Studies, 2022-2026
or-rabinowitz_headshot.jpg

Or (Ori) Rabinowitz  joined Stanford’s Freeman Spogli Institute for International Studies in summer 2026 as a Senior Research Scholar, with appointments at both CDDRL’s Jan Koum Israel Studies Program and CISAC. She arrives at Stanford following her time as a tenured Senior Lecturer (Associate Professor) in the Department of International Relations at the Hebrew University of Jerusalem.

A recipient of the British Foreign Office’s Chevening Scholarship, Rabinowitz completed her PhD in the Department of War Studies at King’s College London in 2011. Her first book, Bargaining on Nuclear Tests, was published by Oxford University Press in 2014. Her second book, Protecting the Nuclear Monopoly, forthcoming with Cambridge University Press, examines the evolution of U.S.–Israeli collaboration in countering nuclear proliferation in the Middle East. Rabinowitz has published widely in leading academic journals as well as in prominent policy and public-facing outlets. She is the recipient of multiple grants and distinctions, including two competitive personal grants from the Israel Science Foundation.

CV
Date Label
Paragraphs

Image
Cover of the book 'The China Questions 2'
The belief that China presents a challenge, if not an outright threat, to U.S. national security is increasingly prevalent in elite and public discourse. The main points of contention lie in the degree to which China threatens U.S. national security, how exactly China may challenge U.S. national security, and uncertainty about how the answers to these questions may change over time (which is fundamentally a debate about the drivers of Chinese strategy).

In this chapter, included in the volume The China Questions 2: Critical Insights into US-China Relations​ Harvard University Press, 2022), Oriana Sklayar Mastro focuses on the direct and indirect ways the People's Republic of China poses a threat to U.S. national security today.

Two caveats are in order. First, this focused discussion on challenges and threats may distort the degree to which China threatens the United States. On aggregate, the discussion presents a malign influence from the Perspective of U.S. national security. But it could be much worse. China has resolved many of its territorial disputes peacefully. Beijing has relied mainly on economic and political tools to blunt U.S. influence beyond its immediate region. China is an active member of the vast majority of international institutions. Even though faced with a conventionally superior U.S. military, China has yet to change its minimal no-first-use nuclear doctrine.

Second, while Mastro presents information on trends and trajectories, her focus is on today's challenges. These are likely to expand in scope and increase in intensity over the next five to ten years.

All Publications button
1
Publication Type
Book Chapters
Publication Date
Subtitle

A chapter in The China Questions 2: Critical Insights into US-China Relations, edited by Maria Adele Carrai, Jennifer Rudolph, and Michael Szonyi.

Authors
Oriana Skylar Mastro
Book Publisher
Harvard University Press
Authors
Oriana Skylar Mastro
News Type
Commentary
Date
Paragraphs

This commentary originally appeared in The Economist.


In the afternoon of August 4th, the People’s Liberation Army (PLA) kicked off the largest and most sophisticated military exercises it has ever conducted. Over the course of a week, the Chinese launched dozens of missiles and conducted drills near Taiwan with 100 aircraft, ten destroyers and support vessels. Submarines and aircraft carriers also played a role. The display has made the third Taiwan Strait crisis, which occurred between 1995-96, when China conducted four rounds of tests over the course of several months, with barrages of no more than six missiles, look like child’s play.

Part of the rationale for the latest exercise was to signal Beijing’s anger over Nancy Pelosi’s visit to Taiwan. Ms Pelosi, the speaker of the House of Representatives, was the highest-ranking American government official to visit the island since 1997. Back then Newt Gingrich, who was also the House speaker, made the trip. China warned that if Ms Pelosi added Taipei to her itinerary, there would be hell to pay.

The exercise is also a bit of a “coming-out party” for Beijing. In 1996 the third crisis ended when America sent two aircraft-carrier strike groups within 200 miles (322km) of Taiwan. America saw this as a great strategic success, and Chinese leaders were unhappy with its interference in what China considers a domestic affair. The resentment helped to drive China to build the PLA into one of the greatest armed forces in the world.


Subscribe to APARC newsletters to receive our experts' analysis and commentary.


Compared with 1996, China’s forces today are barely recognizable. Back then it had a large army, with roughly 4m people, but that was a sign of its backwardness more than anything else. With obsolete equipment and poor training, China barely had what could be considered an air force and a navy. Its pilots could not fly over water, at night or in rough weather. In 1999 less than 2% of its fighters were fourth generation, just 4% of its attack submarines were classed as modern (nuclear powered, for example) and none of its surface ships was. Its navy was a glorified coastguard with ships that, lacking air-defense systems, had to hug the coastline on any patrol. Its nuclear weapons, solid-fuelled and housed mainly in fixed silos, could have been taken out in one fell swoop by America.

Now China’s armed forces are comparable to America’s in quality and quantity. Most of its platforms are modern (of the latest technology for the relevant domain) and it boasts the largest navy in the world. In some areas, Chinese military capabilities already surpass America’s—in shipbuilding, land-based conventional ballistic and cruise missiles, and integrated air-defense systems. China possesses the world’s third-largest nuclear arsenal in the world, one that is currently undergoing major modernization.

Chinese leaders knew the PLA had to conduct a series of large, realistic exercises to identify issues and hone their capabilities. If China had done so out of the blue, instead of using Ms Pelosi’s visit as a pretext, international opprobrium would have been stronger.

But even with all these improvements, it is unclear whether China could take Taiwan by force. China has not fought a war since 1979, when it made heavy weather of a “punitive” invasion of Vietnam. An amphibious attack, and to a lesser degree a blockade of the type the exercises off Taiwan were simulating, would demand complex joint operations (involving army, air force and navy), which in turn require impeccable logistics and command and control. Xi Jinping, China’s leader, launched a massive organizational reform to improve in these areas, and the PLA undoubtedly has. But the war in Ukraine may have given him heightened anxiety, given that the Russians struggled precisely with logistics and command.

For this reason, we should see the massive exercises off Taiwan less as a signal, and more as a rehearsal for combat. Mr Xi wants progress on the Taiwan issue, and domestically talk in the press is shifting from peaceful reunification to armed reunification. Chinese leaders knew the PLA had to conduct a series of large, realistic exercises to identify issues and hone their capabilities. If China had done so out of the blue, instead of using Ms Pelosi’s visit as a pretext, international opprobrium would have been stronger.

China will seize the opportunity to practice as much as possible. It has announced already that this round of exercises will continue and that another round in the Bohai Gulf/Yellow Sea is next. And it won’t just be large-scale exercises. It is unlikely that Beijing will return to its previous level of operations. Instead, China might attempt to normalize greater Chinese activity around Taiwan. That makes war more probable. Through a series of exercises the PLA, and the party leadership, might gain confidence that China’s forces are ready to take Taiwan sooner than they would otherwise have thought.

Of course, this all depends on how the exercises and operations go. From the outside, this is hard to assess. The missiles landed where they should have in recent days, and there were no accidents. But we don’t know how much and how well different groups are communicating with each other. To prepare for joint operations, air-force units need to operate in close proximity and coordinate with ground troops and amphibious elements. The PLA needs to practice providing supplies, such as prepositioned fuel stocks, and bringing munitions and medical supplies to forward locations such as Fujian, the province directly across the Taiwan Strait.

This is where the real trouble lies. If activities in the vicinity of Taiwan become more routine, not only does this heighten anxiety in Taipei (and probably other regional capitals as well) but it helps to disguise any preparations for a real military campaign. China needs an element of surprise to be able to take Taiwan before America has time to mobilize adequate forces in the region to defend the island. If China’s forces are simulating formations, blockades, attacks, and amphibious landings, it will be harder to decipher when they are preparing for the real thing. Ms Pelosi’s visit has allowed Beijing to move to a new level of military activity unchallenged, which will make it harder for America to defend Taiwan. No signal of America’s commitment to the island can fix that.

Read More

Honor guards prepare to raise the Taiwan flag in the Chiang Kai-shek Memorial Hall square.
Commentary

Biden Says We’ve Got Taiwan’s Back. But Do We?

Many will applaud Mr. Biden for standing up for democratic Taiwan in the face of Chinese threats. But he could be putting the island in greater danger, and the United States may not be able to come to the rescue.
Biden Says We’ve Got Taiwan’s Back. But Do We?
An Island that lies inside Taiwan's territory is seen with the Chinese city of Xiamen in the background.
Commentary

The Taiwan Temptation

Why Beijing Might Resort to Force
The Taiwan Temptation
Hero Image
A Taiwanese F-5 fighter jet is seen after taking off from Chihhang Air Base on August 06, 2022 in Taitung, Taiwan.
A Taiwanese F-5 fighter jet is seen after taking off from Chihhang Air Base on August 06, 2022 in Taitung, Taiwan. Taiwan remained tense after U.S. Speaker of the House Nancy Pelosi's visit to the island as part of a tour of Asia aimed at reassuring allies in the region. China has been conducting live-fire drills in waters close to those claimed by Taiwan in response. | Annabelle Chih/ Getty Images
All News button
1
Subtitle

Nancy Pelosi’s visit was more pretext than provocation.

Date Label
Paragraphs

The Institute recently received new information and feedback, warranting a major revision to our report, “Abadeh is Marivan,” first published on August 28, 2020. The Abadeh site is the Amad Plan’s Marivan site, an important test site responsible for conducting large-scale high explosive tests for developing nuclear weapons under the Amad Plan, Iran’s effort during the early 2000s to build five nuclear weapons, subsequently reoriented to a smaller, better camouflaged nuclear weapons effort. The new information allowed the Institute to locate with high certainty Marivan’s outdoor test site, located about 1.5 kilometers northeast from the support site (see Figure 1). Although the logistical support site was razed in July 2019, the outdoor test site appears to have remained largely intact. Recent satellite imagery acquired and analyzed by the Institute shows that the outdoor site features two bunkers and a test ramp.he Institute recently received new information and feedback, warranting a major revision to our report, “Abadeh is Marivan,” first published on August 28, 2020. The Abadeh site is the Amad Plan’s Marivan site, an important test site responsible for conducting large-scale high explosive tests for developing nuclear weapons under the Amad Plan, Iran’s effort during the early 2000s to build five nuclear weapons, subsequently reoriented to a smaller, better camouflaged nuclear weapons effort. The new information allowed the Institute to locate with high certainty Marivan’s outdoor test site, located about 1.5 kilometers northeast from the support site (see Figure 1). Although the logistical support site was razed in July 2019, the outdoor test site appears to have remained largely intact. Recent satellite imagery acquired and analyzed by the Institute shows that the outdoor site features two bunkers and a test ramp.

Read more at The Institute for Science and International Security.

All Publications button
1
Publication Type
Reports
Publication Date
Authors
Frank Pabian
Paragraphs

The Institute of Science and International Security’s new book Iran’s Perilous Pursuit of Nuclear Weapons chronicles the Islamic Republic of Iran’s efforts to build nuclear weapons. The book draws from original Iranian documents seized by Israel’s Mossad in 2018 in a dramatic overnight raid in Tehran. The “Nuclear Archive” allows deep insight into the country’s effort to secretly build nuclear weapons. The book relies on unprecedented access to archive documents, many translated by the Institute into English for the first time. Based on three years of intensive research and analysis of the Nuclear Archives, this new book from the Institute presents a compelling account of Iran’s secret plans to develop nuclear weapons. The Institute of Science and International Security’s new book Iran’s Perilous Pursuit of Nuclear Weapons chronicles the Islamic Republic of Iran’s efforts to build nuclear weapons. The book draws from original Iranian documents seized by Israel’s Mossad in 2018 in a dramatic overnight raid in Tehran. The “Nuclear Archive” allows deep insight into the country’s effort to secretly build nuclear weapons. The book relies on unprecedented access to archive documents, many translated by the Institute into English for the first time.

Read more at the Institute for Science and International Security.

All Publications button
1
Publication Type
Books
Publication Date
Subtitle

Based on three years of intensive research and analysis of the Nuclear Archives, this new book from the Institute presents a compelling account of Iran’s secret plans to develop nuclear weapons. Frank was the Geospatial Contributing Analyst.

Authors
Frank Pabian
Subscribe to Security