WASHINGTON (Reuters) - U.S.-based cyber firm Symantec SYMC.O is no longer allowing governments to review the source code of its software because of fears the agreements would compromise the security of its products, Symantec Chief Executive Greg Clark said in an interview with Reuters.

Tech companies have been under increasing pressure to allow the Russian government to examine source code, the closely guarded inner workings of software, in exchange for approvals to sell products in Russia.

Symantec’s decision highlights a growing tension for U.S. technology companies that must weigh their role as protectors of U.S. cybersecurity as they pursue business with some of Washington’s adversaries, including Russia and China, according to security experts.

While Symantec once allowed the reviews, Clark said that he now sees the security threats as too great. At a time of increased nation-state hacking, Symantec concluded the risk of losing customer confidence by allowing reviews was not worth the business the company could win, he said.

The company’s about-face, which came in the beginning of 2016, was reported by Reuters in June. Clark’s interview is the first detailed explanation a Symantec executive has given about the policy change.

In an hour-long interview, Clark said the firm was still willing to sell its products in any country. But, he added, “that is a different thing than saying, ‘Okay, we’re going to let people crack it open and grind all the way through it and see how it all works’.”

While Symantec had seen no “smoking gun” that foreign source code reviews had led to a cyberattack, Clark said he believed the process posed an unacceptable risk to Symantec customers.

“These are secrets, or things necessary to defend (software),” Clark said of source code. “It’s best kept that way.”

Because Symantec’s market share was still relatively small in Russia, the decision was easier than for competitors heavily invested in the country, Clark said.

FILE PHOTO - Greg Clark, Chief Executive Officer of Symantec, takes part in the Yahoo Finance All Markets Summit in New York, U.S., February 8, 2017. REUTERS/Lucas Jackson

“We’re in a great place that says, ‘You know what, we don’t see a lot of product over there’,” Clark said. “We don’t have to say yes.”

Symantec’s decision has been praised by some western cyber security experts, who said the company bucked a growing trend in recent years that has seen other companies accede to demands to share source code.

“They took a stand and they put security over sales,” said Frank Cilluffo, director of the Center for Cyber and Homeland Security at George Washington University and a former senior homeland security official to former President George W. Bush.

“Obviously source code could be used in ways that are inimical to our national interest,” Cilluffo said. “They took a principled stand, and that’s the right decision and a courageous one.”

Reuters last week reported that Hewlett Packard Enterprise (HPE) HPE.N allowed a Russian defense agency to review the inner workings of cyber defense software known as ArcSight that is used by the Pentagon to guard its computer networks.

HPE said such reviews have taken place for years and are conducted by a Russian government-accredited testing company at an HPE research and development center outside of Russia. The software maker said it closely supervises the process and that no code is allowed to leave the premises, ensuring it does not compromise the safety of its products. A spokeswoman said no current HPE products have undergone Russian source code reviews.

ArcSight was sold to British tech company Micro Focus International Plc MCRO.L in a sale completed in September.

On Monday, Micro Focus said the reviews were a common industry practice. But the company said it would restrict future reviews of source code in its products by “high-risk” governments, and that any review would require chief executive approval.

“SLIPPERY SLOPE”

Earlier this year, Beijing enacted a cyber security law that foreign business groups have warned could adversely impact trade because of its data surveillance and storage requirements. The law has further fueled concern that companies increasingly need to choose between compromising security to protect business or risk losing out on potentially lucrative markets.

Clark said Symantec had not received any requests to review source code from the Chinese government, but indicated he would not comply if Beijing made such a demand.

“We just have taken a policy decision to say, ‘Any foreign government that wants to read our source code, the answer is no’,” Clark said.

The U.S. government does not generally require source code reviews before purchasing commercially available software, according to security experts.

“As a vendor here in the United States,” Clark said, “we are headquartered in a country where it is OK to say no.”

Some security experts fear heightened requests may further splinter the tech world, leading to an environment where consumers and governments only feel safe buying products made in their own countries.

“We are heading down a slippery slope where you are going to end up balkanizing (information technology), where U.S. companies will only be able to sell software to parts of Europe,” said Curtis Dukes, a former head of cyber defense at the National Security Agency now with the non-profit Center for Internet Security, “and Russia won’t be able to sell products in the U.S.”