Google removed a Chrome plugin that was revealed to have been used by white supremacists to track Jews online.

A harmless sounding Google Chrome plugin was pulled from the company’s web store on Thursday, after it was revealed this week by Tech Mic that it was being used by white supremacists to track Jews online.

The “Coincidence Detector” plugin served one purpose, the report said: “Compiling and exposing the identities of Jews and others who are perceived as ‘anti-White.’” Using a special web construction called an “(((echo)))” — three parentheses around the names of targets — white supremacists were able to encase the names of Jews that appeared on a web page. This allowed users to single out popular Jewish personalities in entertainment, media and politics and harass them online, especially on Twitter.

Each new Jewish or anti-white personality identified by the extension was then added to a database of names which was updated regularly. According to the report, with a single click, users were able to refresh the plugin and make sure their own personal list was reflected in the database. If a user believed that (((echo))) excluded the name of an “anti-white” Jew, they were able to submit the name using the “Support” tab.

The extension, which was uploaded by “altrightmedia” — a nod to the emerging far-Right movement made up of young, tech-savvy white supremacists known — was downloaded by 2,473 users and had a rating of five out of five stars. According to a description posted by the uploader, the plugin “can help you detect total coincidences about who has been involved in certain political movements and media empires.” The description echoes conspiracy theories such as that claiming the Jews run the world.

While the extension had remained relatively unknown, its true use came to light when Twitter user @CyberTrump tweeted to New York Times Washington deputy editor Jonathan Weisman: “Hello (((Weisman))),” following his posting of an anti-Trump article. When Weisman asked @CyberTrump to explain the symbol, he wrote, “It’s a dog whistle, fool. Belling the cat for my fellow goyim.” According to Tech Mic, “With the parentheses, @CyberTrump had alerted an army of trolls.”

Oren Segal, director of the Anti-Defamation League Center on Extremism, told Tech Mic that throughout the current election campaign, there has been a significant “spike in hate speech and the harassment of journalists, in particular Jewish journalists.” Segal attributes a large part of this surge to the “xenophobic and Islamophobic rhetoric and policy proposals” of Republican presidential hopeful Donald Trump’s supporters, the report said.