Secure file-sharing software company Kiteworks is urging customers worldwide to temporarily shut down their servers on Saturday for a six-hour window after receiving threat intelligence warning of a potentially imminent cyberattack.

According to German technology publication Heise, Kiteworks CISO Frank Balonis emailed customers warning that the company had received "credible threat intelligence from law enforcement indicating an attack on Kiteworks systems may be imminent this weekend."

"We strongly recommend you shut down your Kiteworks system for six hours," the notification reportedly states.

Heise says the shutdown window applies to customers worldwide, with affected time zones ranging from Australian Eastern Standard Time (AEST) to Pacific Daylight Time (PDT).

In Central Europe, customers were instructed to shut down Kiteworks systems between 4:00 a.m. and 10:00 a.m. on Saturday, September 26. In New York, the shutdown window would be from 10:00 p.m. Friday to 4:00 a.m. Saturday.

The company reportedly recommends shutting down the servers before the scheduled window and says customers should take systems offline even if they are not directly accessible from the Internet.

The company confirmed the warning to BleepingComputer, stating it received intelligence from federal authorities that a threat actor may attempt to target some customer systems.

"Kiteworks received credible threat intelligence from federal intelligence authorities indicating that a threat actor may attempt to target some Kiteworks systems for customers," the company told BleepingComputer.

"Out of an abundance of caution, we notified customers directly and recommended a precautionary shutdown window while we and our law enforcement partners work through the matter."

Kiteworks stressed that the warning is precautionary rather than a response to a confirmed breach.

"We are not aware of any compromise of Kiteworks systems, and this advisory is preventative rather than a response to a confirmed breach," the company said.

"All known vulnerabilities are addressed in our current release, 9.5.1, and we continue to recommend customers run the latest version."

Potential zero-day concerns

While Kiteworks has not confirmed that attackers are exploiting an unknown vulnerability, Heise reports that Kiteworks customer support said the shutdown recommendation is intended to protect customers against potential zero-day attacks.

"The reason we're asking you to shut down the servers is to protect against any potential zero-day attacks," Kiteworks support reportedly told Heise when the publication contacted the company to verify the warning.

However, neither the statement provided to BleepingComputer nor the customer notification quoted by Heise confirms that a zero-day vulnerability has been discovered or exploited.

Instead, Kiteworks says all currently known vulnerabilities are fixed in version 9.5.1 and describes the shutdown as a precaution based on intelligence received from authorities.

Kiteworks develops secure file-transfer and communications products used by government organizations, financial institutions, and enterprises.

Because secure file-sharing platforms commonly store sensitive documents, they are a valuable target for cybercriminals who conduct data-theft extortion attacks.

While it is not known which threat actor is linked to these potential attacks, the Clop extortion gang has a long history of targeting enterprise platforms in data-theft attacks, including Accellion FTA, GoAnywhere MFT, SolarWinds Serv-U FTP, Cleo, and MOVEit Transfer.

The U.S. Department of State now offers a $10 million reward for any information linking the cybercrime gang's attacks to a foreign government.

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