BERLIN (Reuters) - The German foreign ministry has restricted use of the video conferencing service Zoom to fixed-connection computers due to concerns about security issues, two German government sources said.

FILE PHOTO: The Zoom Video Communications logo is pictured at the NASDAQ MarketSite in New York, New York, U.S., April 18, 2019. REUTERS/Carlo Allegri

The decision is directed at use of Zoom on mobile devices using the company’s app, said one of the sources, adding that confidential conversations were not to be carried on videoconferences because they were not comprehensively encrypted.

Zoom is seeing record use as coronavirus lockdown rules force millions of people to work or follow school lessons from home, but on Wednesday hired a top Facebook security executive in response to concerns about the security of its system.

The ministry adopted the restriction, also reported by the Handelsblatt newspaper, after concluding that Zoom’s software had “critical” weaknesses.

One of the German government sources said employees had been instructed to use teleconferences to conduct their business.

The second source said the German government had no uniform position on the use of Zoom and every ministry had its own policies. Certain exceptions could be made to the foreign ministry restrictions during the current crisis, the source added.

A memo to employees cited by the paper said that, “based on media reports and our own findings, we have concluded that Zoom’s software has critical weaknesses and serious security and data protection problems”.

But since the system was in widespread use among the ministry’s international partners, the memo said it was currently impossible to ban its use entirely.

“Zoom takes user security extremely seriously,” a spokesman said in an e-mailed statement. “Zoom is in communication with governments around the world and is focused on providing the information they need to make informed decisions about their policies.”

Taiwan has also told officials to stop using Zoom, while Switzerland has advised them to use Microsoft Teams, not Zoom, as a fallback option if its main provider Skype for Business becomes overloaded, a spokesman said.

Malefactors have managed to gatecrash Zoom video calls, seize control of shared screens and post offensive content, a phenomenon known as “zoombombing”.