The U.S. Commerce Department on Wednesday blacklisted Israel’s NSO Group and Candiru for allegedly selling spying software to foreign governments that used the device to target government officials, journalists and others.

Positive Technologies of Russia and Computer Security Initiative Consultancy PTE LTD of Singapore have also been blacklisted.

Companies blacklisted face reduced exports to these countries by their U.S counterparts, making it much harder for U.S. security researchers to provide information about computer vulnerabilities.

A spokesperson from NSO expressed dismay at the move, saying the company’s technologies “support U.S. national security interests and policies by preventing terrorism and crime, and thus we will advocate for this decision to be reversed.”

On the other hand, sanctions have also been imposed on Positive Technologies, a Russian cybersecurity company, for supporting Russian security services.

Positive Technologies expressed confidence that the new sanctions will not affect its business and will not delay the company’s planned listing on the stock exchange.

A former U.S. official, who spoke on condition of anonymity, said the company had helped build a computer infrastructure used by Russian cyberattacks on U.S. organizations.

Export control experts say the blacklist could have far-reaching implications for companies other than limiting their access to U.S. technology.