When the U.S. and Israel launched attacks against Iran earlier this year, Tehran responded by striking energy infrastructure across the Gulf. The result was a severe shock to global energy markets that continues to this day. Less publicized at the time were its strikes on another kind of infrastructure: data centers.

Similar attacks have since taken place in Russia and Ukraine, where both sides have been trading tit-for-tat strikes on data centers. 

Experts say these attacks represent a new front in warfare, in which facilities powering the technology behind many critical industries have become military targets. 

Read more: How the Iran War Could Threaten Global Internet Access

The AI boom has led to a surge in demand for computing power, data storage and cloud services, making the data centers that provide them a crucial part of modern infrastructure. A mass of data center construction is currently underway in the U.S., and tech companies are investing hundreds of billions of dollars a year to meet AI demand. Telecommunications companies, banks, hospitals and energy suppliers all rely on them. 

“Data centers are now on the critical path for modern digital infrastructure,” Kirk Cameron, founding director of the Institute for Advanced Computing at Virginia Tech, tells TIME. “The loss of key data centers could collapse economies, disrupt public and private transportation with loss of GPS, and affect government essential services for health, emergency dispatch, and power grids.” 

Military use of AI for targeting and information processing has made data centers crucial to fighting a war. Ukraine uses AI for an array of battlefield functions such as drone targeting, battle planning, and missile analyzing Russian missile attacks. U.S. tech companies such as Palantir now work closely with Ukraine’s military to develop new AI-powered weaponry, taking advantage of the ability to immediately test their technology on the battlefield. The U.S. military also uses Palantir’s Maven system to help identify targets for strikes. 

“Data centers are competitive advantages in warfare,” Cameron says. “Knocking out capabilities means potentially crippling combat operations for an adversary. It’s also a form of economic warfare and could lead to longer-term competitive challenges for the target.”

Where have data centers been attacked? 

The first wave of attacks on data centers was carried out in March this year by Iran, when it launched strikes on two Amazon facilities in the United Arab Emirates (UAE) and another in Bahrain was damaged by a nearby drone strike.

Those facilities have been mostly offline ever since; Amazon said on Sept. 15 that it had been “unable to restore access to the resources and data” hosted in those two regions.

Russian attacks on Ukrainian data centers in late September disrupted television broadcasts and internet access. Russia’s Defense Ministry said it was striking data centers because they “process and transmit intelligence data for the Ukrainian Armed Forces.” 

Ukraine’s response began on Oct. 8, and it has since carried out drone strikes on three data centers belonging to tech giant Yandex, often called Russia’s version of Google. The first site hit, in Sasovo, houses two of the three supercomputers Yandex uses to develop its AI models, Meduza reported, and the outage disrupted several companies relying on Yandex’s cloud services, including Russian Railways, MegaFon, T-Bank, and several media outlets. 

Following the first strike, Ukrainian President Volodymyr Zelensky defended the retaliation: "We always respond in kind. You all know that they are hitting and hitting our data centers; we responded to them.”

How have tech companies responded? 

The spate of attacks over the last year has already caused tech companies to rethink how and where they build data centers. 

The United Arab Emirates is reportedly revising plans for a 5-gigawatt AI data center project following the Iranian strikes. The original plan envisioned a 10-square-mile campus in Abu Dhabi, to be built in partnership with American tech companies like Oracle, Nvidia, and Cisco. Now the data centers will likely be spread out across the UAE, according to officials who spoke to Reuters.

Emily Harding, director of the Intelligence, National Security, and Technology Program at the Center for Strategic and International Studies, believes that data centers have become a new frontline in warfare—and that may require new strategies. 

“If you’re Russia and you attack a Microsoft data center, is that an attack on Ukraine? Is that an attack on Microsoft? Is that an attack on a U.S. company and, by extension, the U.S.?” she asks. 

The U.S. has largely followed a policy that attacks on American companies do not constitute an attack on the United States, but Harding says the government may need to decide on a new approach “that creates deterrence not just to protect life and health, but also data.” 

And while the threat to data centers in the U.S. may be relatively low compared to the Gulf and Ukraine or Russia, tech companies will also have to think more about the security of their facilities when building, while trying to keep pace with massive demand. 

“The knock-on effect is that the companies that own the data centers are realizing they can't protect them, and that kind of calls into question the cloud model in general,” Harding says. “They're having to make big adjustments. You could see a time in the future where Amazon starts losing business to Microsoft because Microsoft does a better job of hiding where their data centers are.”