Microsoft called out as big malware hoster – thanks to OneDrive and Office 365 abuse

guest · Oct 19, 2021

Microsoft called out as big malware hoster – thanks to OneDrive and Office 365 abuse
Infosec pro: 'OneDrive abuse has been going on for years'
October 18, 2021
https://www.theregister.com/2021/10/18/microsoft_malware_brand/

Microsoft has been branded as "the world's best malware hoster for about a decade," thanks to abuse of the Office 365 and Live platform, as well as its slow response to reports by security researchers.

Infosec expert Kevin Beaumont, who worked at Microsoft as a senior threat intelligence analyst between June 2020 and April 2021, made the comments in response to a report by "cybersec professional" TheAnalyst.
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TheAnalyst noted that a BazarLoader malware campaign was hosting its malware on Microsoft's OneDrive service. "Does Microsoft have any responsibility in this when they KNOWINGLY are hosting hundreds of files leading to this, now for over three days?" they asked.

"Amusingly, while at MS we built a pipeline to alert Google Drive about Bazarloader to have the links taken down, hence why it happened so quickly (literally minutes). Now they've moved to Microsoft infrastructure, who have the pipeline, but can't get Office to remove the files," said Beaumont.
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A site called URLhaus, maintained by Swiss project abuse.ch at the Bern University Institute for Cybersecurity and Engineering, keeps statistics on how long it takes for malware to be removed by the site which hosts it.
The latest statistics show that Microsoft has the worst reaction time of any in the top ten sites hosting the most malware urls, at over 29 days.

The official Twitter account of abuse.ch, which runs URLhaus, said "for the record, the oldest active malware site with an age of 19 months is hosted on Sharepoint and serving GuLoader."
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The Microsoft sites hosting malware use OneDrive accounts that might have been created specifically for the purpose, or hijacked from legitimate users.
Even if malware is detected by Microsoft Defender, it is not "automatically taken down in OneDrive," Beaumont said.

The message for users is that seeing a link is hosted on a familiar name like OneDrive or Google Drive is not a reason to have confidence that it is safe to open - and that allow-listing those domains is a mistake.
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Microsoft called out as big malware hoster – thanks to OneDrive and Office 365 abuse

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