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

Infosec pro: 'OneDrive abuse has been going on for years'


Updated 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.

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.

BazarLoader is a family of malware where a spam email attempts to trick recipients into opening a trojan via a link, in this case to an ISO (disk image that can be mounted with one click) containing a malicious DLL with a misleading shortcut called Documents that runs it, leading in time to a potential ransomware attack using Conti.

"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.

Adding to the misery, "Microsoft's documentation specifically tells you to allowlist domains in question so security solutions don't inspect the content. Try defending a business with a situation like this," challenged Beaumont.

He added that "Microsoft cannot advertise themselves as the security leader with 8,000 security employees and trillions of signals if they cannot prevent their own Office365 platform being directly used to launch Conti ransomware. OneDrive abuse has been going on for years."

Average reaction time to malware reports: Microsoft is among the worst, and Google is also very poor

Average reaction time to malware reports: Microsoft is among the worst, and Google is also very poor

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.

According to the figures, Google hosts more malware and is also slow to remove it, but with a 14-day response time it is twice as quick as Microsoft.

Malware hosted on OneDrive, reported to URLhaus

Malware hosted on OneDrive, reported to URLhaus

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." It added: "I've seen an increase of 10 new malware sites hosted at MS over the weekend. Whatever they do with these reports filled out through the MSRC API, it is definitely not automated." MSRC is the Microsoft Security Response Center.

Beaumont said that while "My experience is the Azure Storage items should disappear very quickly ... unfortunately Office is in a mess"

The Microsoft sites hosting malware use OneDrive accounts that might have been created specifically for the purpose, or hijacked from legitimate users. It is also common to see malware hosted on business Office 365 accounts that have been compromised.

Automated blocking of suspicious files by the cloud providers is problematic not only because new variants are hard to detect, but also for privacy reasons. Even if malware is detected by Microsoft Defender, it is not "automatically taken down in OneDrive," Beaumont said.

The reaction time measures how long it takes to remove malicious content following a specific report, and is an average time to remove the malware; the full list shows that some reports take just two days and others up to 4 months.

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.

We have asked Microsoft for comment.®

Updated on 19 October to add:

A Microsoft spokesperson said: "Abuse of cloud storage is an industry-wide issue and we're constantly working to reduce the use of Microsoft services to cause harm. We are investigating further improvements to prevent and rapidly respond to the types of abuse listed in this report." They added: "We continue to encourage customers to practice good computing habits online, including exercising caution when clicking on links to web pages, opening unknown files, or accepting file transfers, and we also encourage customers to report abuse using this form [link]."

Similar topics


Other stories you might like

  • It's primed and full of fuel, the James Webb Space Telescope is ready to be packed up prior to launch

    Fingers crossed the telescope will finally take to space on 22 December

    Engineers have finished pumping the James Webb Space Telescope with fuel, and are now preparing to carefully place the folded instrument inside the top of a rocket, expected to blast off later this month.

    “Propellant tanks were filled separately with 79.5 [liters] of dinitrogen tetroxide oxidiser and 159 [liters of] hydrazine,” the European Space Agency confirmed on Monday. “Oxidiser improves the burn efficiency of the hydrazine fuel.” The fuelling process took ten days and finished on 3 December.

    All eyes are on the JWST as it enters the last leg of its journey to space; astronomers have been waiting for this moment since development for the world’s largest space telescope began in 1996.

    Continue reading
  • China to upgrade mainstream RISC-V chips every six months

    Home-baked silicon is the way forward

    China is gut punching Moore's Law and the roughly one-year cadence for major chip releases adopted by the Intel, AMD, Nvidia and others.

    The government-backed Chinese Academy of Sciences, which is developing open-source RISC-V performance processor, says it will release major design upgrades every six months. CAS is hoping that the accelerated release of chip designs will build up momentum and support for its open-source project.

    RISC-V is based on an open-source instruction architecture, and is royalty free, meaning companies can adopt designs without paying licensing fees.

    Continue reading
  • The SEC is investigating whistleblower claims that Tesla was reckless as its solar panels go up in smoke

    Tens of thousands of homeowners and hundreds of businesses were at risk, lawsuit claims

    The Securities and Exchange Commission has launched an investigation into whether Tesla failed to tell investors and customers about the fire risks of its faulty solar panels.

    Whistleblower and ex-employee, Steven Henkes, accused the company of flouting safety issues in a complaint with the SEC in 2019. He filed a freedom of information request to regulators and asked to see records relating to the case in September, earlier this year. An SEC official declined to hand over documents, and confirmed its probe into the company is still in progress.

    “We have confirmed with Division of Enforcement staff that the investigation from which you seek records is still active and ongoing," a letter from the SEC said in a reply to Henkes’ request, according to Reuters. Active SEC complaints and investigations are typically confidential. “The SEC does not comment on the existence or nonexistence of a possible investigation,” a spokesperson from the regulatory agency told The Register.

    Continue reading

Biting the hand that feeds IT © 1998–2021