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
Newest First  |  Oldest First  |  Threaded View
Crowdsourced vs. Traditional Pen Testing
Alex Haynes, Chief Information Security Officer, CDL,  3/19/2019
BEC Scammer Pleads Guilty
Dark Reading Staff 3/20/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: Well, at least it isn't Mobby Dick!
Current Issue
5 Emerging Cyber Threats to Watch for in 2019
Online attackers are constantly developing new, innovative ways to break into the enterprise. This Dark Reading Tech Digest gives an in-depth look at five emerging attack trends and exploits your security team should look out for, along with helpful recommendations on how you can prevent your organization from falling victim.
Flash Poll
The State of Cyber Security Incident Response
The State of Cyber Security Incident Response
Organizations are responding to new threats with new processes for detecting and mitigating them. Here's a look at how the discipline of incident response is evolving.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-9923
PUBLISHED: 2019-03-22
pax_decode_header in sparse.c in GNU Tar before 1.32 had a NULL pointer dereference when parsing certain archives that have malformed extended headers.
CVE-2019-9924
PUBLISHED: 2019-03-22
rbash in Bash before 4.4-beta2 did not prevent the shell user from modifying BASH_CMDS, thus allowing the user to execute any command with the permissions of the shell.
CVE-2019-9925
PUBLISHED: 2019-03-22
S-CMS PHP v1.0 has XSS in 4.edu.php via the S_id parameter.
CVE-2019-9927
PUBLISHED: 2019-03-22
Caret before 2019-02-22 allows Remote Code Execution.
CVE-2019-9936
PUBLISHED: 2019-03-22
In SQLite 3.27.2, running fts5 prefix queries inside a transaction could trigger a heap-based buffer over-read in fts5HashEntrySort in sqlite3.c, which may lead to an information leak. This is related to ext/fts5/fts5_hash.c.