Microsoft Teams vulnerability shows danger of collaboration apps

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Microsoft Teams is perhaps the biggest enterprise communication platform in the world. It rose to prominence during the COVID-19 pandemic as a key space for enterprise users to maintain productivity.

Teams has over 270 million monthly active users. The pandemic helped accelerate the platform’s reach from 75 million users in April 2020 to 115 million in October 2020, and 145 million in April 2021.

Overall, Gartner recorded a 44% rise in workers’ use of collaboration tools since 2019, to the point where 80% of workers were using collaboration tools for work in 2021.

While these tools are convenient, their widespread use has opened the door to some serious vulnerabilities. 


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For example, according to research released by Vectra yesterday, versions of Teams for Windows, Mac and Linux are storing authentication tokens in plain text on the underlying device. This is significant because it means if an attacker hacks a system where Teams is installed they can gain access to authentication tokens along with other information. 

This vulnerability highlights that enterprises can’t afford to rely on the security of consumer-grade, public-grade communication platforms when they’re communicating sensitive information, IPs and other data. 

How bad is the Microsoft Teams vulnerability?  

This isn’t the first time that collaboration tools like Teams have received criticism for being insecure. At the start of this year, Avanan identified a significant uptick in cyberattacks taking place over Microsoft Teams, with threat actors using chats and channels to circulate malicious .exe files. 

These new vulnerabilities are another chink in the armor of applications that aim to be enterprise-grade communication platforms.

“In essence, this is still [the] unsolved problem of stealing cookies and other web credentials by attackers with local access,” said John Bambenek, principal threat hunter at Netenrich. “That isn’t to say it’s not significant. The fundamental problem is that attackers can steal a cookie and use it on any number of machines to replay an authenticated machine.”

“I would like to see developers and tech companies send these credentials hashed with some local-machine specific information so cookie and credential relay attackers would disappear entirely,” Bambenek added. 

The problem with collaboration apps 

Collaboration apps aren’t immune to vulnerabilities. Like any piece of browser-based software, they have underlying bugs and can be targeted with web-based attacks and phishing attempts. 

Just recently it emerged that a bug in Slack had exposed some users’ hashed passwords over a period of five years. That came roughly a year after attackers used stolen cookies to hack EA Games’ personal communication channel, allegedly stealing 780GB of data including the Fifa 21 source code. 

The problem isn’t that solutions like Slack or Microsoft are particularly weak, but that they’re not optimized to keep up with the level of sophisticated threats targeting modern organizations from both cybercriminals and state-sponsored actors. 

In spite of these weaknesses, many organizations continue to share protected information through these channels. According to Veritas Technologies, 71% of office workers globally admit to sharing sensitive and business-critical company data using virtual collaboration tools. So what can organizations do? 

Limiting the risk of collaboration apps  

Vectra reported the new Teams vulnerability to Microsoft in August, but the latter disagreed that the severity of the vulnerability warranted patching. 

In any case, enterprises processing and managing trade secrets or regulated information need to be cautious about using communication apps that put high-value data at risk of exposure. That doesn’t mean they should stop using communication apps completely. But it does mean they should implement robust controls to reduce the risk of data leakage. 

As one Deloitte report notes, “collaboration technologies, while vital during the surge of virtual work, can pose serious threats to organizational security and privacy if not properly managed. As these technologies expand their reach and prevalence in business operations, organizations should keep a pulse on potential threats, enact controls where feasible, and promote service availability.” 

In practice, controls include using select strong randomized passwords, using cloud access security broker (CASB) solutions to identify data exfiltration, implementing content guidelines for platforms, and deploying a web application firewalls to detect application layer attacks.

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