Vulnerabilities / Threats
12/13/2016
05:05 PM
Connect Directly
Twitter
LinkedIn
RSS
E-Mail
50%
50%

Microsoft Patches Dangerous Backdoor In Skype For Mac OS X

Vulnerability would have let attackers record calls, intercept and read messages, and siphon out all kinds of data, Trustwave says.

Microsoft has patched a backdoor in Skype for Mac OSX that would allow an attacker to log and record Skype call audio, retrieve user contact information, read the content of incoming messages, create chat sessions, modify messages, and carry out other malicious activity.

The backdoor provided nearly complete access without authentication to Skype on OS X, and appears to have been around since at least 2010, security vendor Trustwave said in an advisory this week.

The vulnerability seems to have been created by a developer at Skype prior to Microsoft’s takeover of the company, and likely exposed some 30 million Mac OS X users.

Trustwave described the backdoor as a locally exploitable issue in the Skype Desktop API for Mac OS-X that gave any program, including malware, unauthenticated access to the API.

The vulnerable Application Programming Interface has been discontinued and is being slowly phased out in versions of Skype across all platforms.

The backdoor appears to have been put in place to enable older versions of the Skype Dashboard Widget plugin to access the Desktop API without user interaction, says a researcher from the UK pen testing team at Trustwave’s SpiderLab, who requested anonymity. What makes this a very likely possibility is the fact that the Desktop API provides for a client named “Skype Dashbd Wdgt Plugin.”

The widget is a small program that runs on the OS-X Dashboard and is designed to let users make Skype calls from the Dashboard by entering a number.  

Interestingly, though, there is no indication that the widget itself actually used the backdoor to access the Desktop API, according to Trustwave. So it is possible the backdoor is the result of code being accidentally left behind when the widget was being implemented. "It is likely the backdoor was used at some time in the past but fell into disuse and just got left there," the researcher says.

The result was that local programs had unauthenticated access to the Desktop API as long as the programs used "Skype Dashbd Wdgt Plugin" as their client name identifier, the researcher says. 

Trustwave described the backdoor as easy to access and requiring little more than a simple change to the client application name to "Skype Dashbd Wdgt Plugin." Once this was done, the API made no attempt to determine what programs were accessing it - making it trivially easy for attackers to slip in malware.

"There was no means for the user to deny access via the backdoor," the researcher says. "In older versions of OS-X and Skype, the user was not informed at all if the backdoor was being used, in later versions, potentially sometime around OS-X 10.9-10, a notification was present, but the user still did not have the ability to deny access."

The Desktop API in previous versions of Skype permitted access to almost everything within the application so attackers could take complete control by abusing the backdoor.  So "[an] attacker could write a piece of code into their malware to siphon every piece of info you could think of from Skype" including contact lists, instant messages, and conversations, the researcher says.

Related stories:

 

Jai Vijayan is a seasoned technology reporter with over 20 years of experience in IT trade journalism. He was most recently a Senior Editor at Computerworld, where he covered information security and data privacy issues for the publication. Over the course of his 20-year ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Threaded  |  Newest First  |  Oldest First
Register for Dark Reading Newsletters
Dark Reading Live EVENTS
INsecurity - For the Defenders of Enterprise Security
A Dark Reading Conference
While red team conferences focus primarily on new vulnerabilities and security researchers, INsecurity puts security execution, protection, and operations center stage. The primary speakers will be CISOs and leaders in security defense; the blue team will be the focus.
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: No, no, no! Have a Unix CRON do the pop-up reminders!
Current Issue
Security Vulnerabilities: The Next Wave
Just when you thought it was safe, researchers have unveiled a new round of IT security flaws. Is your enterprise ready?
Flash Poll
The Impact of a Security Breach 2017
The Impact of a Security Breach 2017
Despite the escalation of cybersecurity staffing and technology, enterprises continue to suffer data breaches and compromises at an alarming rate. How do these breaches occur? How are enterprises responding, and what is the impact of these compromises on the business? This report offers new data on the frequency of data breaches, the losses they cause, and the steps that organizations are taking to prevent them in the future.
Slideshows
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2017-0290
Published: 2017-05-09
NScript in mpengine in Microsoft Malware Protection Engine with Engine Version before 1.1.13704.0, as used in Windows Defender and other products, allows remote attackers to execute arbitrary code or cause a denial of service (type confusion and application crash) via crafted JavaScript code within ...

CVE-2016-10369
Published: 2017-05-08
unixsocket.c in lxterminal through 0.3.0 insecurely uses /tmp for a socket file, allowing a local user to cause a denial of service (preventing terminal launch), or possibly have other impact (bypassing terminal access control).

CVE-2016-8202
Published: 2017-05-08
A privilege escalation vulnerability in Brocade Fibre Channel SAN products running Brocade Fabric OS (FOS) releases earlier than v7.4.1d and v8.0.1b could allow an authenticated attacker to elevate the privileges of user accounts accessing the system via command line interface. With affected version...

CVE-2016-8209
Published: 2017-05-08
Improper checks for unusual or exceptional conditions in Brocade NetIron 05.8.00 and later releases up to and including 06.1.00, when the Management Module is continuously scanned on port 22, may allow attackers to cause a denial of service (crash and reload) of the management module.

CVE-2017-0890
Published: 2017-05-08
Nextcloud Server before 11.0.3 is vulnerable to an inadequate escaping leading to a XSS vulnerability in the search module. To be exploitable a user has to write or paste malicious content into the search dialogue.