Lawsuit argues Amazon illegally surveilled NYC customers including tracking their body size. Here's why Amazon Go stores are watching you.

• Amazon Go stores, which have no cashiers, use a system of cameras and tech to track customers.
• A new lawsuit alleges the company's stores in New York City illegally collect data on customers' size and shape without telling them.

Customers at Amazon Go stores are tracked using a system of cameras, sensors, and motion detection software to create a shopping experience free from cashiers and checkout lines — but a new lawsuit is arguing that the company never really told New York City customers that they're being surveilled.

The class action lawsuit filed this week claims that Amazon collected data on the shape and size of customers' bodies — and even scans of some customers' hands — without proper warning.

"From the moment a person walks through the door … Amazon uses computer vision to track people," Peter Roman-Friedman, lead attorney on the lawsuit, told Insider.

The lawsuit pertains specifically to nine Amazon's Go stores in New York City, where city law says companies must disclose when customers' biometric data is being collected. Still, Roman-Friedman said he hopes the lawsuit catches the eye of lawmakers on other local and federal levels.

In a statement to Insider, the company stressed that it does not use facial recognition software in its stores — although the New York lawsuit does not mention facial recognition in its complaints.

The company also challenges the notion that the technology it uses to track customers inside the store constitutes biometric data — which is defined broadly under city law as a physiological or biological characteristic that is used to identify an individual.

The data is crucial to the high-tech stores' ability to charge customers for the items they want without employing a cashier. Amazon creates skeleton-like models based on people's size and shape, according to the lawsuit, which mirror the real movements customers make inside the store.

"[T]he Just Walk Out technology used to distinguish shoppers from one another is not biometric, and is used only to link a customer with their purchases during a single store visit," an Amazon spokesperson told Insider Saturday.

Amazon had failed to post signs at its New York stores addressing biometric data for over a year, putting them in place this week — after the New York Times reported their absence, according to the lawsuit. The new signs say no biometric data is being collected outside use of the palm scanner, according to the lawsuit.

"Only shoppers who choose to enroll in Amazon One and choose to be identified by hovering their palm over the Amazon One device have their palm-biometric data securely collected, and these individuals are provided the appropriate privacy disclosures during the enrollment process," the spokesperson said.

Amazon Go customers must use an app or credit card linked to their Amazon account, or the store's palm scanner, to enter the store. Shoppers then pick up the items they want to purchase, and Amazon tracks the items taken by customers before charging them automatically as they leave the store.

The lawsuit also claims the new signs at Amazon Go stores are designed with colors, style, and fonts that make them easier to ignore.

"We think that Amazon's conduct has gone from bad to worse," Roman-Friedman told Insider.