“That was the first time I had a real indication that I was on some kind of list,” the ex-Meta employee told Business Insider. 

Meta’s former employees and managers confirmed that the $1.5 trillion tech giant tracks what ex-employees are available to rehire, stamping them with “non-regrettable attrition” or “do not hire” designations. This creates barriers for hiring managers to consider certain candidates who have worked at the business before. 

Some former workers told Business Insider they were restricted from rejoining Meta, despite carrying records of quality job performance. A spokesperson for Meta told Fortune: “It is false that those who leave ‘in good standing’ are not eligible for rehire based on ‘internal lists’ or ‘manager discretion.'”

The spokesperson went on to say that Meta determines the reason for a staffer’s departure—including policy violation, performance termination, and voluntary resignation—alongside their most recent rating to assess the ability of rehire. They added that if someone is marked ineligible for rehire, there is a checks-and-balances system so a manager cannot tag an individual without support.

Workplace experts tell Fortune discreet ‘block lists’ are on the rise—especially in competitive industries like the one Meta is weathering. 

Block lists: Meta’s not alone—they’ve been around for decades

While most companies keep their ‘block lists’ under wraps, the news of Meta’s practice opened the floodgates on how pervasive the blacklisting is. In a Reddit thread responding to Business Insider’s reporting, users divulged that they—or people they know—have had the same experience.

“Amazon insists if you get fired, they will never rehire you,” ConnectionIssues alleged in the comment thread. “I know someone who took the buyout and went to work for Whole Foods. When Amazon bought [Whole Foods], he was told to find other work.”

Another commenter alleged that Amazon, Google, Microsoft, and more all have ‘block lists.’ In response to Google allegedly having a ‘block list,’ Courtenay Mencini, a spokesperson for Google, told Fortune “This is not true.” Based on experts’ statements and social media sharing, a common thread stands out: technology giants are more prone to blacklist former employees. Or at least they’re being called out on it more than others. Amazon and Microsoft have not responded to Fortune‘s requests for comment.

“It’s hard to know how prevalent block lists have been in the past, but it’s definitely something we’re seeing more often now, particularly in the tech industry,” Jennifer Dulski, CEO of management software company Rising Team, tells Fortune. “Whether or not block lists are common, most companies have a concept of ‘regretted’ and ‘non-regretted attrition.’”

There are a few reasons why a former staffer may wind up on an employer’s block list—including “activist” behavior, poor performance, and inappropriate workplace behavior. But there are also factors out of a worker’s control: new leadership having different tastes, or no longer being the right fit for a company’s shifted culture. And experts say there’s a clear sign of being put on the naughty list—being ghosted by hiring managers early on, as was the case of the ex-Meta employee. But the bold can also be straight-up, and ask the interviewer if they’re eligible for rehire. 

Being put on a ‘block list’ can feel like a break-up with an employer—and experts say it can be best to see it that way, and move on. But there are also a few tricks workers can employ to get back in the good graces of their former companies. 

“[Block lists have] been around for decades but have recently evolved,” Patrice Lindo, CEO of professional coaching business Career Nomad, tells Fortune. “In today’s digital-first HR environments, these lists are embedded in shared databases, making them more persistent—and in many cases, more damaging.” 

What behaviors put employees on a block list

Workers may feel blindsided by being put on a ‘block list’—but experts point to a few key employee behaviors that can spur such a negative reaction.

Dulski and others point to the obvious: poor performance, sexual misconduct, bullying, and illegal behavior are understable reasons why workers get banned from rehire. But there are more discreet workplace-related tensions at play. 

“It’s possible that at some companies, ‘activist’ behavior—like speaking out against company policies, decisions, values, etc.—could get someone on a block list,” Dulski says. 

This could be a heightened issue among companies like Meta, that have driven unfavorable policies among workers—like the recent “low performer” layoffs. One of the company’s workers even wrote that “Meta is now the cruelest tech company out there” following tense job cuts. The software company isn’t the only employer to ruffle the feathers of staffers. Other tech companies have been in hot water with staffers over their leadership choices. 

“Employees who speak out against toxic leadership, demand better working conditions, or even resign abruptly during key initiatives are often blacklisted quietly,” Lindo says. “Ironically, the same behaviors that demonstrate leadership and integrity can be perceived as threats in toxic cultures.”

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But businesses don’t always choose to hear out the concerns of disgruntled employees; workforce changes become an echo-chamber of “what’s best for business.” Large corporations contend that change, no matter how unpopular, is needed to drive efficiency and company culture. Experts say that evolving approaches in leading businesses could alter who is considered the right “fit” under new commands. 

“What puts people on a block list is dependent on the company culture and leadership, and can change overtime, particularly if there’s a changing of the guard in the C-suite,” Dulski says.

How to know you’re on a company’s naughty list—and if you can get off

It can be hard to tell if you’re on a ‘block list’—former employees aren’t notified that they’re barred from being rehired. But experts say there’s one surefire to know. 

“Block lists and non-regretted attrition lists are rarely published and almost never shared with the individuals affected,” Dulski says. “One way someone could find out if they are on a block list is when they are denied interviews early in the process, seemingly without any explanation.”

But staffers can save themself the trouble of trial-and-error applying. Rebecca Trotsky, chief people officer at HR Acuity, tells Fortune that workers questioning their status could simply ask. 

“One way to find out is to contact your previous employer and ask about your rehire status,” she says. “They could also ask at the time of exit whether they’ll be considered eligible for rehire in the future.”

And for those who end up on their former employer’s blacklist, there are a few options at hand. Dulski says she views block lists as “bad romantic breakups,” and generally advises job-seekers to have that perspective and find a company that’s a stronger fit. But for staffers who can’t get over it—and are vying to get back into the good graces of an ex-boss—there’s a strategy they can deploy. Lindo lays out a three-point plan: rebrand, network, and achieve recognition.

“Control the story. Publicly showcase your evolution and results—through updated résumés, thought leadership, and your digital footprint,” she says. “Build authority by sharing your expertise. Apply for awards, speak on panels, or publish. Visibility builds validity.”