Identity-theft vulnerability fixed in Microsoft Office 365, says security firm

Microsoft has plugged a vulnerability in Microsoft Office 365 that would have let attackers grab user identities and steal email and documents, according to Adallom, the security vendor that says it discovered the problem.

"What we found is if you sent a link to a user by email and the user opens the document, the attacker gets access to the user's tokens," says Ami Luttwak, co-founder and CTO at Adallom. The security firm that informed Microsoft about the software-as-a-service (SaaS) vulnerability, which it says took a few months to fix because of its complexity.

+ MORE ON NETWORK WORLD Cloud Security Alliance offers ultra-high cloud security plan +

Luttwak says the Office 365 "tokens" in question are the means for authentication to log into Office 365 and gain access to applications like Word or Excel. "In a general sense, it's an identity theft attack," he says. Before it was fixed, the attacker could access SaaS-based documents through any device and upload and download them at will, he says.

According to Luttwak, the token-stealing problem was basically a wider "problem with the Microsoft ecosphere" that would impact Microsoft Office 365, SharePoint and SkyDrive. Luttwak said this newer type of security problem in the cloud goes beyond Microsoft Office 365 and in fact, Adallom is working with other vendors to identify and fix similar vulnerabilities found in their SaaS applications.

Ellen Messmer is senior editor at Network World, an IDG publication and website, where she covers news and technology trends related to information security. Twitter: MessmerE. E-mail:

Read more about wide area network in Network World's Wide Area Network section.

Join the CSO newsletter!

Error: Please check your email address.

Tags securityMicrosoftcloud security allianceendpoint securityanti-malwareWide Area Network

More about ExcelIDGMicrosoft

Show Comments

Featured Whitepapers

Editor's Recommendations

Solution Centres

Stories by Ellen Messmer

Latest Videos

  • 150x50

    CSO Webinar: The Human Factor - Your people are your biggest security weakness

    ​Speakers: David Lacey, Researcher and former CISO Royal Mail David Turner - Global Risk Management Expert Mark Guntrip - Group Manager, Email Protection, Proofpoint

    Play Video

  • 150x50

    CSO Webinar: Current ransomware defences are failing – but machine learning can drive a more proactive solution

    Speakers • Ty Miller, Director, Threat Intelligence • Mark Gregory, Leader, Network Engineering Research Group, RMIT • Jeff Lanza, Retired FBI Agent (USA) • Andy Solterbeck, VP Asia Pacific, Cylance • David Braue, CSO MC/Moderator What to expect: ​Hear from industry experts on the local and global ransomware threat landscape. Explore a new approach to dealing with ransomware using machine-learning techniques and by thinking about the problem in a fundamentally different way. Apply techniques for gathering insight into ransomware behaviour and find out what elements must go into a truly effective ransomware defence. Get a first-hand look at how ransomware actually works in practice, and how machine-learning techniques can pick up on its activities long before your employees do.

    Play Video

  • 150x50

    CSO Webinar: Get real about metadata to avoid a false sense of security

    Speakers: • Anthony Caruana – CSO MC and moderator • Ian Farquhar, Worldwide Virtual Security Team Lead, Gigamon • John Lindsay, Former CTO, iiNet • Skeeve Stevens, Futurist, Future Sumo • David Vaile - Vice chair of APF, Co-Convenor of the Cyberspace Law And Policy Community, UNSW Law Faculty This webinar covers: - A 101 on metadata - what it is and how to use it - Insight into a typical attack, what happens and what we would find when looking into the metadata - How to collect metadata, use this to detect attacks and get greater insight into how you can use this to protect your organisation - Learn how much raw data and metadata to retain and how long for - Get a reality check on how you're using your metadata and if this is enough to secure your organisation

    Play Video

  • 150x50

    CSO Webinar: How banking trojans work and how you can stop them

    CSO Webinar: How banking trojans work and how you can stop them Featuring: • John Baird, Director of Global Technology Production, Deutsche Bank • Samantha Macleod, GM Cyber Security, ME Bank • Sherrod DeGrippo, Director of Emerging Threats, Proofpoint (USA)

    Play Video

  • 150x50

    IDG Live Webinar:The right collaboration strategy will help your business take flight

    Speakers - Mike Harris, Engineering Services Manager, Jetstar - Christopher Johnson, IT Director APAC, 20th Century Fox - Brent Maxwell, Director of Information Systems, THE ICONIC - IDG MC/Moderator Anthony Caruana

    Play Video

More videos

Blog Posts