Twitter has banned ads on its service from Russian security software maker Kaspersky Lab, after the U.S. government prohibited agencies from using its products because of alleged ties to the Russian government.
The ban, confirmed by Twitter to Reuters, marks an escalation of the backlash against Kaspersky Lab, which has come under intense scrutiny over the past year.
In December of 2017, President Donald Trump signed a law banning U.S. agencies from using Kaspersky Lab security software, which came several months after the U.S. Department of Homeland Security issued a ban on the software for all federal agencies.
“The Department is concerned about the ties between certain Kaspersky officials and Russian intelligence and other government agencies, and requirements under Russian law that allow Russian intelligence agencies to request or compel assistance from Kaspersky and to intercept communications transiting Russian networks,” the Department of Homeland Security said in a statement. “The risk that the Russian government, whether acting on its own or in collaboration with Kaspersky, could capitalize on access provided by Kaspersky products to compromise federal information and information systems directly implicates U.S. national security.”
Kaspersky Lab has denied any links to the Russian government, and in late 2017 announced a series of transparency initiatives that include an independent review of its source code, and opening “transparency centers” in Asia, the U.S., and Europe between 2018 and 2020.
On Friday, Kaspersky Lab CEO Eugene Kaspersky shared a screenshot on Twitter of what he says is a letter from an “unnamed Twitter employee,” who explained that the company’s ads were banned from Twitter because it “operates using a business model that inherently conflicts with acceptable Twitter Ads business practices.” Kaspersky said the company learned of the ban in January.
“I read this formulation again and again but still couldn’t for the life of me understand how it might relate to us,” Kaspersky said about the letter. “One thing I can say for sure is this: we haven’t violated any written – or unwritten – rules, and our business model is quite simply the same template business model that’s used throughout the whole cybersecurity industry: We provide users with products and services, and they pay us for them.
He continued: “In my view, the ban itself contradicts Twitter’s declared-as-adopted principle of freedom of expression.”
In January, another social media company, Facebook, told Congress in a statement that “In October 2017, we removed Kaspersky’s anti-virus software from the list of products that we make available to these users.”
Fortune contacted Kaspersky Lab and Twitter for further comment and will update this post if it receives a response.