To score a table at Don Angie, the Italian-American hotspot in New York’s West Village, the official course of action is to log on to restaurant booking site Resy at 9 a.m. seven days before the desired dining date. At least, that’s the policy that chef-owners Angie Rito and Scott Tacinelli have set up for potential diners.

But those who have recently tried to book those elusive seats via the reservation platform know they rarely open up.

If you head over to Appointment Trader, however, and are willing to pay up to $125 just for the opportunity to walk through the door, you can start bidding on seats for any day for the next few weeks.

The issue of seats disappearing that should be available began last summer, says Rito. “But it has become more pronounced over the last few months.”

She believes that bots—software programs engineered to perfect certain tasks, like swiping up Taylor Swift tickets or restaurant reservations the millisecond seats open up—are mostly to blame.

The operators behind those seat-snatching programs then try to make a quick buck—or several hundred—by reselling the reservations on sites like Appointment Trader. The two-year-old website enables individuals to buy and sell restaurant bookings and finds seats using bots as well as concierges and other people with access to restaurants.

Owners at several other of New York’s hard-to-get-into restaurants, from downtown Indian haunts Dhamaka and Semma to tiny Farra Wine Bar in Tribeca, and the revamped new American spot Virginia’s, also report being burned by bots. “We have noticed certain names making a large amount of reservations, and either no-showing or having different guests utilizing them,” says Isabella Pisacane, a partner and director of hospitality at French bistro Libertine. “Certain guests will appear trepidatious when approaching the maitre’d when checking in, as they’re not using their actual names.”

“It is a very serious issue now, happening to a lot of restaurants and bars,” says GN Chan, co-owner of Double Chicken Please in the Lower East Side and ranked No. 2 on the World’s 50 Best Bars list. He notes that the bar began receiving brokered reservations from bots soon after the drinking den was named the best bar in North America earlier this year.

Em Pak, a manager at Double Chicken Please, says that there are some signature ways to tell if a seat has been booked by a bot: Resy accounts may be connected to invalid email addresses comprised of jumbled numbers and letters, or profiles with a history of booking prime time, back-to-back reservations on weekends — such as 7 p.m. reservations every Friday and Saturday for several weekends. Others are the usual disconnected phone numbers attached to bookings and invalid credit cards.

But even though they may suspect suspicious activity in advance, Pak admits that a lot of the time they don’t know for sure, “and we don’t want to risk canceling a reservation that belongs to someone who authentically booked.”

This means that not only does the business miss out on the $20 cancellation fee charged to invalid credit cards, the bar loses time, and eventually customers and revenue, when they hold bot seats that go unfilled.

But Chan—who has seen seats at his bar selling for $340 each on six-month-old Cita marketplace, another website that enables diners to buy and sell restaurant reservations—calls out another issue. When guests drop $100 or more just to walk in the door, “people have [the] wrong expectation when they come” he says because those expectations might be unreasonably high.

Pak says that Resy, which runs the reservations for Double Chicken Please and is owned by American Express, has taken action: They are “deleting confirmed bot profiles and sending what are essentially cease and desist emails to broker profiles,” she says. The actions have helped, Pak adds, but the issue persists. Now, Double Chicken Please has cut down on the number of reserved seats they offer and are welcoming more walk-ins.

A spokesperson for Resy says that the company is taking measures to block bot-booking. “Resy detects and deactivates bad actor accounts, cancels reservations, and blocks bot traffic,” they said over email.

At Tock, another reservation site that books tables at notable restaurants around the world, there’s an in-house Fraud Prevention team that uses a proprietary algorithm to flag suspicious activity. It has used it to block cards and scalper accounts a handful of times. Two months ago, the company added verification techniques to block bots, that include having users check boxes to verify they are real people. Resy also uses a variety of checks, including checking boxes and two-factor authentication for profiles.

Some new sites are testing out their own bot workarounds. ResX, a six-month-old app that began as an Instagram account, is free to use and provides a platform for diners to give away and claim restaurant reservations. For $10 a month, ResX also offers access to what it calls “premium” restaurants, like the power pasta dining spot Misi in Brooklyn. Users earn “tokens” by giving away their reservations; the tokens, in turn, can be used to claim premium reservations.

Longtime ResX user Jake Andrew, who declined to give his last name, has used the app to avoid cancellation charges. That includes trading a table for 8 at Montauk’s Surf Lodge last summer — the definition of valuable culinary real estate in the Hamptons. “I was going to be charged $400, $50 per guest,” he says.

Another new members-only app, Dorsia, works with restaurants to score prime reservations at places like the supper club space 9 Jones and even the impossible-to-get-into Carbone in New York. (The site, whose name has a clear American Psycho connection, also covers cities like Miami, London, the Bay Area and Los Angeles restaurants.)

But a diner must agree to a certain prepaid per-person spend when they book: For example, dinner at Cote Korean Steakhouse might cost $125 per person on a weekday night at 5 p.m.; on a weekend at 9 p.m. that figure might be $175. The benefit is that, although the seats might cost more, the extra money goes to a diner’s food and drinks as opposed to a reseller’s pocket.

For now, the only solution for frustrated restaurateurs is “a lot of added time and effort,” says Don Angie’s Rito. She and her staff are currently reaching out to every customer on Don Angie’s waitlist one-by-one to ensure that they’re a real person who will walk through the door of the restaurant and into a seat.