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.

Network Security

09:35 AM
Larry Loeb
Larry Loeb
Larry Loeb

Fidelis Researchers Demo Dangerous Covert Channel in Digital Certificates

Researchers at Fidelis have found a way to exploit a flaw in the X.509 certificate protocol to create a covert data exchange channel.

Researchers at Fidelis have found a covert channel that malware can import and export data through the Transport Layer Security (TLS) protocol. This new channel works from industry standard X.509 certificate protocols, and can sneak under network perimeter protections by seeming to be normative network traffic.

The channel occurs during the certificate exchange in a TLS handshake. It does not require that a TLS session ever be established, only that the handshake that is preliminary is to be the one being negotiated.

The data that is actually exchanged will show up in the extensions to the certificate. Fidelis Security Systems Inc. researchers found that they were able to store 60 kilobytes of data in each TLS X.509 exchange.

A proof-of-concept was published on Monday, February 5, along with a technical explanation.

While the idea of using a covert channel inside a protocol has been examined in the past, Fidelis researcher Jason Reaves published his take on using X.509 certificates in this manner in January.

In his summary, Reaves wanted to:

Demonstrate that we can take some lessons from the other areas of cyber security research, namely exploitation, and look at potential use cases in how malware authors could utilize technologies outside of their intended purposes to not only accomplish their goals but also end up bypassing common security measures in the process.

Reaves seems to have succeeded in that task.

First, he gives code examples of how such data may be placed, as well as exfiltrated. Once he got that working, he tested out the scheme.

The fundamentals of network security are being redefined -- don't get left in the dark by a DDoS attack! Join us in Austin from May 14-16 at the fifth-annual Big Communications Event. There's still time to register and communications service providers get in free!

Reaves then found that only SSL negotiations, which could bypass common security mechanisms that are not looking for abnormal data being passed in x509 certificates, occurred.

The proof-of-concept used the case of a malicious binary -- the credential sniffer was Mimikatz -- being transferred in the clear via this method. What was done was to simulate a threat actor transferring Mimikatz to an already compromised system. It went through just fine.

One way to mitigate the proof-of-concept might be to check for executable files within binaries. Another could be blocking any self-signed certificates at the perimeter boundary.

The good news, if there is any, is that the Fidelis teams say that they have not found this attack being used in the wild. But, with the proof-of-concept now out, we cannot be so confident that some threat actor will not try it soon.

Related posts:

— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting

Comment  | 
Print  | 
More Insights
Newest First  |  Oldest First  |  Threaded View
I Smell a RAT! New Cybersecurity Threats for the Crypto Industry
David Trepp, Partner, IT Assurance with accounting and advisory firm BPM LLP,  7/9/2021
Attacks on Kaseya Servers Led to Ransomware in Less Than 2 Hours
Robert Lemos, Contributing Writer,  7/7/2021
It's in the Game (but It Shouldn't Be)
Tal Memran, Cybersecurity Expert, CYE,  7/9/2021
Register for Dark Reading Newsletters
White Papers
Current Issue
Enterprise Cybersecurity Plans in a Post-Pandemic World
Download the Enterprise Cybersecurity Plans in a Post-Pandemic World report to understand how security leaders are maintaining pace with pandemic-related challenges, and where there is room for improvement.
Flash Poll
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
PUBLISHED: 2021-09-22
Leo Editor v6.2.1 was discovered to contain a regular expression denial of service (ReDoS) vulnerability in the component plugins/importers/dart.py.
PUBLISHED: 2021-09-22
CMS Made Simple 2.2.14 was discovered to contain a cross-site scripting (XSS) vulnerability which allows attackers to execute arbitrary web scripts or HTML via a crafted payload in the Field Definition text field.
PUBLISHED: 2021-09-22
gmate v0.12+bionic contains a regular expression denial of service (ReDoS) vulnerability in the gedit3 plugin.
PUBLISHED: 2021-09-22
The vCenter Server contains a local privilege escalation vulnerability due to the way it handles session tokens. A malicious actor with non-administrative user access on vCenter Server host may exploit this issue to escalate privileges to Administrator on the vSphere Client (HTML5) or vCenter Server...
PUBLISHED: 2021-09-22
The vCenter Server contains a denial-of-service vulnerability due to improper XML entity parsing. A malicious actor with non-administrative user access to the vCenter Server vSphere Client (HTML5) or vCenter Server vSphere Web Client (FLEX/Flash) may exploit this issue to create a denial-of-service ...