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.

Endpoint //

Authentication

1/12/2015
03:37 PM
Connect Directly
Twitter
RSS
E-Mail
100%
0%

'Skeleton Key' Malware Bypasses Active Directory

Malware lets an attacker log in as any user, without needing to know or change the user's password, and doesn't raise any IDS alarms.

Network monitoring software or abnormal user behavior are two ways to detect an attacker within your network, but new malware dubbed "Skeleton Key" can evade both.

The new malware, discovered by Dell SecureWorks Counter Threat Unit (CTU), can bypass Active Directory systems that only use single-factor authentication. As the researchers explain in analysis released today: "Skeleton Key is deployed as an in-memory patch on a victim's AD domain controllers to allow the threat actor to authenticate as any user, while legitimate users can continue to authenticate as normal."

So the attacker can pose as any user, without needing to steal the user's log-in credentials, and without changing the user's password, thereby soon alerting the helpdesk to a problem when the real user cannot log in.

Skeleton Key does have a few key weaknesses though -- at least in the samples detected by SecureWorks. For one, before an attacker can deploy it, they must already have admin access to the network.

Why bother installing malware to pose as another user when you already have admin access? One use could be to avoid being detected by basic behavior analysis.

“The Skeleton key malware allows the adversary to trivially authenticate as any user using their injected password," says Don Smith, director of technology for the CTU research team. "This can happen remotely for Webmail or VPN. This activity looks like, and is, normal end user activity, so the chances of the threat actor raising any suspicion is extremely low and this is what makes this malware particularly stealthy."

If the attacker poses as a human resources director, then it wouldn't seem abnormal for them to access databases of personally identifiable information. If they pose as a sales director, it wouldn't be suspicious for them to access databases of payment card data. This could be particularly useful to malicious insiders in the IT department who already have admin access.

Skeleton Key's other main drawback is that it does not use any persistence methods. So it must be redeployed any time the domain controller is restarted. As the researchers explain, "Between eight hours and eight days of a restart, threat actors used other remote access malware already deployed on the victim's network to redeploy Skeleton Key on the domain controllers."

One of the things that makes Skeleton Key difficult to find is that it creates no network traffic, and is therefore not going to be detected by network-based monitoring systems like IDS or IPS.

"In the incident response case we outline in the [threat analyis], the adversary was conducting a long-running espionage campaign," Smith says. "This ability allowed them to maintain a very low profile, whereas repeated use of domain credentials to access key documents might tip off the network defenders, whilst Skeleton Key is super-stealthy."

However, deployment of Skeleton Key does trigger domain controller replication issues that researchers say "could not be explained or addressed by Microsoft support and eventually required a reboot to resolve." The lack of a persistence mechanism means that a reboot would effectively kick out the malware; but it could be redeployed later using remote access malware already installed within the organization.

All this, of course, is only effective if the target organization does not employ two-factor authentication. So start there.

Sara Peters is Senior Editor at Dark Reading and formerly the editor-in-chief of Enterprise Efficiency. Prior that she was senior editor for the Computer Security Institute, writing and speaking about virtualization, identity management, cybersecurity law, and a myriad ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
News
US Formally Attributes SolarWinds Attack to Russian Intelligence Agency
Jai Vijayan, Contributing Writer,  4/15/2021
News
Dependency Problems Increase for Open Source Components
Robert Lemos, Contributing Writer,  4/14/2021
News
FBI Operation Remotely Removes Web Shells From Exchange Servers
Kelly Sheridan, Staff Editor, Dark Reading,  4/14/2021
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
2021 Top Enterprise IT Trends
We've identified the key trends that are poised to impact the IT landscape in 2021. Find out why they're important and how they will affect you today!
Flash Poll
How Enterprises are Developing Secure Applications
How Enterprises are Developing Secure Applications
Recent breaches of third-party apps are driving many organizations to think harder about the security of their off-the-shelf software as they continue to move left in secure software development practices.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2021-21070
PUBLISHED: 2021-04-19
Adobe Robohelp version 2020.0.3 (and earlier) is affected by an uncontrolled search path element vulnerability that could lead to privilege escalation. An attacker with permissions to write to the file system could leverage this vulnerability to escalate privileges.
CVE-2020-7851
PUBLISHED: 2021-04-19
Innorix Web-Based File Transfer Solution versuibs prior to and including 9.2.18.385 contains a vulnerability that could allow remote files to be downloaded and executed by setting the arguments to the internal method. A remote attacker could induce a user to access a crafted web page, causing damage...
CVE-2021-29399
PUBLISHED: 2021-04-19
XMB is vulnerable to cross-site scripting (XSS) due to inadequate filtering of BBCode input. This bug affects all versions of XMB. All XMB installations must be updated to versions 1.9.12.03 or 1.9.11.16.
CVE-2021-23381
PUBLISHED: 2021-04-18
This affects all versions of package killing. If attacker-controlled user input is given, it is possible for an attacker to execute arbitrary commands. This is due to use of the child_process exec function without input sanitization.
CVE-2021-23374
PUBLISHED: 2021-04-18
This affects all versions of package ps-visitor. If attacker-controlled user input is given to the kill function, it is possible for an attacker to execute arbitrary commands. This is due to use of the child_process exec function without input sanitization.