Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

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
7 Truths About BEC Scams
Ericka Chickowski, Contributing Writer,  6/13/2019
DNS Firewalls Could Prevent Billions in Losses to Cybercrime
Curtis Franklin Jr., Senior Editor at Dark Reading,  6/13/2019
Can Your Patching Strategy Keep Up with the Demands of Open Source?
Tim Mackey, Principal Security Strategist, CyRC, at Synopsys,  6/18/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
Building and Managing an IT Security Operations Program
As cyber threats grow, many organizations are building security operations centers (SOCs) to improve their defenses. In this Tech Digest you will learn tips on how to get the most out of a SOC in your organization - and what to do if you can't afford to build one.
Flash Poll
The State of IT Operations and Cybersecurity Operations
The State of IT Operations and Cybersecurity Operations
Your enterprise's cyber risk may depend upon the relationship between the IT team and the security team. Heres some insight on what's working and what isn't in the data center.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-2729
PUBLISHED: 2019-06-19
Vulnerability in the Oracle WebLogic Server component of Oracle Fusion Middleware (subcomponent: Web Services). Supported versions that are affected are 10.3.6.0.0, 12.1.3.0.0 and 12.2.1.3.0. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTP to compromise ...
CVE-2019-3737
PUBLISHED: 2019-06-19
Dell EMC Avamar ADMe Web Interface 1.0.50 and 1.0.51 are affected by an LFI vulnerability which may allow a malicious user to download arbitrary files from the affected system by sending a specially crafted request to the Web Interface application.
CVE-2019-3787
PUBLISHED: 2019-06-19
Cloud Foundry UAA, versions prior to 73.0.0, falls back to appending ?unknown.org? to a user's email address when one is not provided and the user name does not contain an @ character. This domain is held by a private company, which leads to attack vectors including password recovery emails sent to ...
CVE-2019-12900
PUBLISHED: 2019-06-19
BZ2_decompress in decompress.c in bzip2 through 1.0.6 has an out-of-bounds write when there are many selectors.
CVE-2019-12893
PUBLISHED: 2019-06-19
Alternate Pic View 2.600 has a User Mode Write AV starting at PicViewer!PerfgrapFinalize+0x00000000000a8868.