WASHINGTON—A network of gig workers world-wide is unwittingly providing basic intelligence to the U.S. military using only a consumer app on their smartphones.

San Francisco-based Premise Data Corp. pays users, many of them in the developing world, to complete basic tasks for small payments. Typical assignments involve snapping photos, filling out surveys or doing other basic data collection or observational reporting such as counting ATMs or reporting on the price of consumer goods like food.

About half of the company’s clients are private businesses seeking commercial information, Premise says. That can involve assignments like gathering market information on the footprint of competitors, scouting locations and other basic, public observational tasks. Premise in recent years has also started working with the U.S. military and foreign governments, marketing the capability of its flexible, global, gig-based workforce to do basic reconnaissance and gauge public opinion.

Premise is one of a growing number of companies that straddle the divide between consumer services and government surveillance and rely on the proliferation of mobile phones as a way to turn billions of devices into sensors that gather open-source information useful to government security services around the world.

The company says 90% of its work is gauging public sentiment and understanding human geography by paying users to fill out surveys, yielding data that it says has uses for commercial businesses, nonprofits and governments. A smaller number of projects, it says, involve asking users to go out into the world to complete tasks such as taking pictures or walking a predetermined route. Sometimes those tasks involve collecting data on nearby wireless signals or other cellphones, the company said, comparing the practice to how Google and Apple map Wi-Fi networks with phones using their operating systems.

“Data gained from our contributors helped inform government policy makers on how to best deal with vaccine hesitancy, susceptibility to foreign interference and misinformation in elections, as well as the location and nature of gang activity in Honduras,” Premise Chief Executive Officer Maury Blackman said. The company declined to name its clients, citing confidentiality.

Premise launched in 2013 as a tool meant to gather data for use in international development work by governments and nongovernmental organizations. In recent years, it has also forged ties to the U.S. national-security establishment and highlighted its capability to serve as a surveillance tool, according to documents and interviews with former employees. As of 2019, the company’s marketing materials said it has 600,000 contributors operating in 43 countries, including global hot spots such as Iraq, Afghanistan, Syria and Yemen.

According to federal spending records, Premise has received at least $5 million since 2017 on military projects—including from contracts with the Air Force and the Army and as a subcontractor to other defense entities. In one pitch on its technology, prepared in 2019 for Combined Joint Special Operations Task Force-Afghanistan, Premise proposed three potential uses that could be carried out in a way that is “responsive to commander’s information requirements”: gauge the effectiveness of U.S. information operations; scout and map out key social structures such as mosques, banks and internet cafes; and covertly monitor cell-tower and Wi-Fi signals in a 100-square-kilometer area. The presentation said tasks needed to be designed to “safeguard true intent”—meaning contributors wouldn’t necessarily be aware they were participating in a government operation.

VIEW Document

A page from a Premise document prepared for U.S.-led coalition forces in Afghanistan shows the distribution of the company’s users there. Click the image to read the entire 29-page document.

The company said the document reflected only potential capabilities and doesn’t accurately characterize the work it does for military clients. A spokesperson for coalition forces in Afghanistan didn’t respond to a request for comment about whether coalition forces ever saw the concept note or had engaged Premise’s services.

A second document, submitted to the Air Force for a grant that the company ultimately received, echoed similar capabilities—with Premise saying it could dispatch workers to do “directed observations, associated sentiment, and wireless network mapping.” Another Premise document says the company can design “proxy activities” such as counting bus stops, electricity lines or ATMs to provide incentives for contributors to move around as background data is gathered.

Data from Wi-Fi networks, cell towers and mobile devices can be valuable to the military for situational awareness, target tracking and other intelligence purposes. There is also tracking potential in having a distributed network of phones acting as sensors, and knowing the signal strength of nearby cell towers and Wi-Fi access points can be useful when trying to jam communications during military operations. Nearby wireless-network names can also help identify where a device is, even if the GPS is off, communications experts say.

Mr. Blackman said gathering open-source data of that nature doesn’t constitute intelligence work. “Such data is available to anyone who has a cellphone,” he said. “It is not unique or secret.”

“If some of our data is used by government departments to shape policy and to protect our citizens, we are proud of that,” he said.

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Premise submitted a document last July to the British government describing its capabilities, saying it can capture more than 100 types of metadata from its contributors’ phones and provide them to paying customers—including the phone’s location, type, battery level and installed apps. A spokesman for the British embassy in Washington didn’t respond to a question about whether any U.K. government agencies were using the service.

Users of the Premise app aren’t told which entity has contracted with the company for the information they are tasked with gathering. The company’s privacy policy discloses that some clients may be governments and that it may collect certain types of data from the phone, according to a spokesman.

Currently the app assigns about five tasks a day to its users in Afghanistan, according to interviews with users there, including taking photos of ATMs, money-exchange shops, supermarkets and hospitals.

At left, a screenshot of the Premise app shows examples of tasks available to a user in Washington, D.C. At right, a sample task the company uses to train new app users, as shown to a user in Afghanistan.

At left, a screenshot of the Premise app shows examples of tasks available to a user in Washington, D.C. At right, a sample task the company uses to train new app users, as shown to a user in Afghanistan.

One user in Afghanistan said he and others there are typically paid 20 Afghani per task, or about 25 cents—income for phone and internet services. A few months ago, some of the tasks on the site struck him as potentially concerning. He said the app posted several tasks of identifying and photographing Shiite mosques in a part of western Kabul populated largely by members of the ethnic Hazara Shiite minority. The neighborhood was attacked several times by Islamic State over the past five years, and militants killed at least 50 people there in May in three explosions targeting a girls’ school, an attack for which no group has claimed responsibility. Because of the nature and location of the tasks in a hot spot for terrorism, the user said he thought those tasks could involve spying and didn’t take them on.

Premise said photographing religious sites such as mosques, temples, synagogues and churches is a standard task assigned to contributors around the world to help clients understand the physical and social geography of a place. Contributors are only asked for exterior photographs and aren’t asked to enter any sites.

None of the more than three million people who have worked with Premise over the past five years has come to harm as they have completed more than 100 million tasks or surveys, the company said.

Premise began as a way to register prices in the developing world and help its customers better understand the needs of the population. But the company struggled to turn a profit in those markets, and the demand for its services was inconsistent, former employees say.

In 2018, the board brought in Mr. Blackman as CEO, hoping he could stabilize the company’s finances and bring in new business, according to current and former employees. Mr. Blackman had experience in the government contracting world, having earlier founded Accela, a company that developed software for government. He pushed to pursue more intelligence and military contracts, the employees said, which led to a culture clash within the company’s workforce, many of them veterans of the development world who objected to some uses of the military and intelligence contracts that were being considered for the platform. A spokesman for the company dismissed that account as coming from disgruntled former employees and said the company hasn’t departed from its original mission. David Soloff, Premise’s co-founder, who preceded Mr. Blackman as CEO, didn’t respond to a request for comment.

In recent years, Premise’s data has been purchased by numerous defense contractors or government agencies working on defense programs, federal records show. The Air Force paid the company $1.4 million in 2019 to do “persistent ground ISR”—a military abbreviation that stands for intelligence, surveillance and reconnaissance. The Air Force Research Laboratory said the contract was focused on data science and machine learning work for military units but declined to provide additional details.

At least five other defense contractors working on intelligence or defense contracts have purchased the data, federal spending records show. Premise stepped up its presence in Washington in recent years, posting jobs requiring security clearances on LinkedIn and bringing on employees whose LinkedIn profiles say they are veterans of the intelligence community.

Write to Byron Tau at byron.tau@wsj.com