Angela Lang/CNET

There's a booming market for apps that track your phone without your knowledge, siphoning off call and text records, photos and more to send to the person who secretly installed the spy app. It's called stalkerware, and according to a poll released on Wednesday by antivirus provider NortonLifeLock, one in 10 Americans admits to using it on their partner's or ex's devices.

Men are more than twice as likely than women to use the apps, according to the poll, which NortonLifeLock conducted in partnership with the Harris Poll. The apps are often marketed as theft protection or child-monitoring tools, said Kevin Roundy, a researcher at NortonLifeLock.

Because the apps run in the background, victims receive no notification that someone has installed stalkerware on their devices. The stealth nature of the apps makes them dangerous, Roundy says, and NortonLifeLock notifies users when the apps are detected.

"It should never be covert about what it's doing," Roundy said, referring to stalkerware technology.

The NortonLifeLock report comes as antivirus companies boost their efforts to detect and track stalkerware. Malwarebytes and Kaspersky look for the apps on customers' devices and have published reports on how often they find them. Academics and advocates are also working with antivirus companies to push for greater awareness of the dangers of stalkerware. All three antivirus companies are part of the Coalition to Stop Stalkerware, as are German antivirus firms Avira and G Data.

The apps fit an odd category of malicious software that can harm users but is sold legally. It's installed by people who know the victims, rather than distant cybercriminals. Roundy said people often use stalkerware when relationships are ending, a time when domestic violence experts say the risk of harm to an abused partner is highest.

Using the apps can violate wiretap and GPS privacy laws and is often part of a pattern of criminal harassment and stalking. But local law enforcement agencies are still catching up with the trend. Eva Galperin of the Electronic Frontier Foundation says education and advocacy are necessary to crack down on the use of stalkerware.

People who buy and install stalkerware on a partner's devices often leave obvious traces, including payment records and IP addresses that could let law enforcement track them down.

"That's very strong evidence they can take action on," Galperin said.

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Though app stores have made progress in removing the apps from their platforms, NortonLifeLock's Roundy said, some apps just rebrand and say they're child safety apps. But as long as they're capable of covertly spying on device users, they're dangerous, he added.

Tracking partners without their consent is also bigger than stalkerware apps, Roundy said. Respondents to the poll said they engaged in several broader behaviors that let them stealthily track partners and exes.

The most common behaviors were checking a partner's phone or browsing history without their consent, with 29% and 21% of respondents respectively saying they did this. Nine percent said they'd created a fake social media profile and sent a friend request to their target's private social media accounts, and 8% had tracked someone's physical activity through fitness apps.

Many respondents also said they didn't think such "creeping" behaviors were a big deal, with 35% saying they weren't concerned as long as they weren't being stalked in person. However, men were much more likely to voice this opinion; 43% of men agreed with the idea, compared with 27% of women.