Britain’s main cyber security agency on Friday warned British government agencies to avoid using anti-virus software from Russian companies, the latest in a series of moves targeting Moscow-based security software maker Kaspersky Lab.

In a letter to departmental permanent secretaries, the director of the UK National Cyber Security Centre, Ciaran Martin, said Russian-made anti-virus software should not be used in systems containing information that would harm national security if it was accessed by the Russian government. He said his agency is in talks with Kaspersky Lab to develop a system for reviewing its products for use in Britain. 

Moscow-based antivirus software maker Kaspersky Lab said on Wednesday that its security software had taken source code for a secret American hacking tool from a personal computer in the United States.

In September, U.S. officials ordered Kaspersky’s products removed from government computers, saying the firm was vulnerable to Kremlin influence and that using the software could jeopardize national security. After that announcement, the Wall Street Journal reported on Oct. 5 that hackers working for the Russian government appeared to have targeted a National Security Agency (NSA) worker by using Kaspersky software to identify classified files in 2015.

The Trump administration on Wednesday told U.S. government agencies to remove Kaspersky Lab products from their networks, saying it was concerned the Moscow-based cyber security firm was vulnerable to Kremlin influence and that using its anti-virus software could jeopardize national security.

The decision represents a sharp response to what U.S. intelligence agencies have described as a national security threat posed by Russia in cyberspace, following an election year marred by allegations that Moscow weaponized the internet in an attempt to influence its outcome. 

Earlier this summer the House Science Committee sent letters to 22 US government agencies requesting information on their use of Kaspersky Lab security products.

As the federal government continues to investigate claims of ties between the Trump administration and Russia, officials in Washington have expressed concern that the government's use of software from Kaspersky Lab—a well-known security vendor based in Russia—could compromise domestic intelligence. This request represents the most recent action in an aggressive campaign by Congress.

U.S. senators sought on Wednesday to ban Moscow-based cyber security firm Kaspersky Lab's products from use by the military because of fears the company is vulnerable to "Russian government influence," a day after the FBI interviewed several of its U.S. employees as part of a probe into its operations.

Federal Bureau of Investigation agents visited the homes of Kaspersky employees late on Tuesday in multiple U.S. cities, although no search warrants were served, according to two sources, who spoke on condition of anonymity because they were not authorized to discuss the FBI probe. 

Russian security software maker Kaspersky Lab has filed antitrust complaints against Microsoft with the European Commission and the German federal cartel office, it said in a statement on Tuesday.

Kaspersky Lab said Microsoft was abusing its dominance in the PC operating system market, creating obstacles for independent software security vendors by distributing its own Defender anti-virus software with the ubiquitous Windows operating system. Microsoft built the anti virus software into Windows, saying this protected users but Kaspersky said it was anti-competitive. Microsoft said in a statement on Tuesday that it had not violated any laws.

Russia’s growing aggression toward the United States has deepened concerns among U.S. officials that Russian spies might try to exploit one of the world’s most respected cybersecurity firms to snoop on Americans or sabotage key U.S. systems.

Products from the company, Kaspersky Lab, based in Moscow, are widely used in homes, businesses and government agencies throughout the United States, including the Bureau of Prisons. Kaspersky Lab’s products are stocked on the shelves of Target and Best Buy, which also sells laptops loaded by manufacturers with the firm’s anti-virus software.

A common security bug affected the antivirus engines of three major vendors, AVG, McAfee, and Kaspersky, as enSilo security researchers have discovered. The problem was first detected back in March 2015, when one of enSilo's own products collided with an AVG antivirus on one of its client's workstations.

After further investigation into the matter, enSilo's staff uncovered a security bug in the AVG antivirus as being the cause of the software incompatibility. The security bug relates to the fact that the AVG antivirus creates a memory space with full RWX privileges where it normally runs. Attackers would be allowed to bypass Windows built-in security features.