Most people looking for a new job — if they currently have one — use their personal email to correspond with a prospective employer. They don’t tell the people they work with they’re being recruited. They slip on a suit jacket for the interview after leaving the office. In other words, they carry out the process in secret.

Or so they think.

A start-up that tracks an individual’s job search activity in public social media accounts is quietly — and some would say creepily — calculating a score it says helps represent how likely each one is to be looking for a job.

The start-up, Joberate, scrapes publicly available data from millions of individual online social media accounts, or buys it from other parties, to assign what it calls a “J-Score” that estimates the level of job search activity, likening it to a FICO score. If the person starts following company accounts on Twitter, clicks through to articles about resume writing or career-related content in their Facebook feed, or begins making a bunch of professional connections on LinkedIn, the score goes up. Joberate then shares these scores with clients — typically to help employers keep tabs on talented outsiders or see how engaged their own workers are in their jobs

Joberate doesn’t see activity that has been set to private, says co-founder and chief executive Michael Beygelman, and it doesn’t pick up on general online searches outside of social media accounts or most activity on job boards.

But if you use an Apply with LinkedIn button on a job posting, comment on a story about job searches that uses Facebook to collect comments, or use some niche industry sites, such as Stack Overflow, that combine aspects of social media and job boards, Joberate could detect your activity and include it as part of your score. The calculation takes into account an individual’s typical social media use and job responsibilities to create a baseline score, and adjusts its calculations accordingly.

“Society has been able to quantify a lot of things about life events,” Beygelman says. But “one thing we don’t really have much understanding of is job search activity. Whenever someone resigned, it was a shock: ‘Oh my god, Mary’s leaving.’ ”

Beygelman’s start-up is part of a growing field of technology tools for human resources departmentsthat use machine learning and mine vast amounts of data to run “predictive analytics” that estimate future workforce needs, such as which current employees might be ready to leave or when a much-coveted external recruit might be ready to listen to a recruiter. As the Harvard Business Review highlighted recently, some companies are even monitoring how often employees swipe their badges in and out of an office building or tracking how much time they spend on career sites from their work computers in order to gauge worker happiness and who might be on their way out. One consultant who follows recruiting trends and technology, CareerXRoads’ Gerry Crispin, puts it this way: “Stalking has become a profession.”

Some say the idea that such social media activity could be tracked in this way could surprise — and concern — consumers.

“I think there’s much greater recognition among consumers that what you post to social media, if it’s not set to being private, can be seen by others,” says Paul Stephens, director of policy and advocacy for the Privacy Rights Clearinghouse. “I don’t think there’s as much awareness that a click stream can be seen by other entities.”

The creep factor makes some human resources professionals hesitant, too. “I have had a lot of conversations about whether it’s creepy or not,” says Lori Hock, chief executive of the Americas for Hudson, a consulting firm. She has even done presentations at H.R. conferences that debated whether such technology was “creepy or competitive,” although she thinks the concerns will dissipate over time.

Beygelman says he can understand the concerns, but he emphasizes that only public data is used. “At the end of the day, anything that’s new is going to make people feel uncomfortable,” he says.

Despite that discomfort, employees may see an upside. Beygelman has one financial services client that is using Joberate to spot when their best employees’ job searching activity spikes, and then sends in internal recruiters to help find them better opportunities in-house.

Another firm has looked at the average job search activity scores of the people who work for different supervisors, Beygelman says, to identify potential problems with managers, rather than employees. In doing so, they found a trouble spot where a recent office move had led to dissatisfaction about long commutes.

However, most of Beygelman’s larger clients — he says he has 14 in the Fortune 100, although he would not reveal any of them — use the software at a macro level, looking only at aggregatescores for employees across a particular division, job site or group to see where there might be trouble spots with how engaged workers are in their jobs. (Beygelman also calculates the average J-Score on his website of all the Fortune 100 companies, whether they’re clients or not, for a “J-Index.” It recently reported that Pfizer had the lowest score and Caterpillar had the highest; the latter did not immediately respond to a request for comment.)

While they may have access to individual workers’ data, most clients don’t use it that way, Beygelman says. “They don’t look at it as ‘aha, I’m going to spy on my people.’ They look at it as ‘I finally know what they’re thinking so I can help them.’ ”

It’s unclear yet how valuable companies will find the data — plenty of workers search for jobs outside their social media accounts, of course. And many people set their accounts to private, particularly if they work at more senior levels. Yet Brian Kropp, who leads human resources consulting for CEB, which has a venture capital arm that’s an investor in Joberate, thinks such tools are likely to grow in use.

“Three to five years from now, my guess is the idea of the annual employee engagement survey will seem like this cute quaint thing we used to do,” he says. “I think it’s just a matter of time before employees start to feel more comfortable with it.”