Every rule has an exception: How to detect insider threat without rules

Andrew Tsonchev, Director of Cyber Analysis | Wednesday June 21, 2017

Typically, security controls have to predefine ‘good’ and ‘bad’ behavior, but this approach inevitably leaves room for people to circumvent those rules, intentionally or otherwise. This is especially problematic when it comes to establishing rules for insiders. Too restrictive, and their workflow is impeded. Too laissez-fair, and they open themselves up to easily preventable threats.

For instance, to prevent anomalous RDP connections – either inbound or outbound – traditional security tools like firewalls often predefine which destination ports to allow and which ports to restrict. However, if an employee were to use a destination port not explicitly restricted by the firewall, they could theoretically exfiltrate data out of the network without raising any alerts.

After installing on the corporate network of a large manufacturing company, our AI technology recently spotted a rogue device making RDP connections to a rare external host that should have been blocked by the firewall.

10.230.102.143 · 00:23:18:28:3d:8c made 2 RDP connections to 100% rare external host mail.klaxcar[.]com

The company’s firewall was configured to prevent outbound RDP connections, but the rule was overly simplistic and was defined by destination port. By changing the port in use, the connections were allowed to continue.

Time: 2017-03-23 14:44:57 [UTC]
Protocol: RDP
Source: 10.230.102.143
Destination: 217.109.48.125
Destination Port: 30005

No other devices in the network had been observed connecting to that host. The activity represented a major deviation from the pattern of normality built by Darktrace’s AI algorithms. The connections lasted over ten minutes and involved the download of nearly 4MB of data.

10.230.102.143 was first seen on the network on 2017-03-23.
Total duration: 10 mins 34 secs
Total upload: 0.19 MB
Total download: 3.77 MB

Darktrace Antigena determined this activity was threatening enough to require an immediate response. It triggered an autonomous response that blocked all outgoing traffic from the device for 10 minutes, giving the security team time to identify the rogue device and stop the RDP activities.

Upon investigation, it became clear that an employee had connected their personal device to the corporate network and was attempting to send valuable intellectual property to a foreign party. The external host happened to be associated with a competing manufacturing company.

It may be tempting to conclude that the company simply needed a better firewall, but that misses the point. Legacy tools – no matter how expensive – still rely on rules, and every rule has an exception. Of course, firewalls are still an essential part of modern cyber security, but organizations need to accept that cyber-threats will always find a way around these tools.

At Darktrace, our technology doesn’t make any assumptions about maliciousness. It uses advanced machine learning and AI algorithms to learn ‘normal’ for every user and device on a network. When a threatening deviation arises, Darktrace neutralizes the threat in real time. While some of these anomalies get stopped by firewalls and other rules-based tools, subtle insider threats like these frequently go undetected.

To learn more about the threats Darktrace finds, check out our Threat Use Cases page which tells the story of how a hacker compromised the video conferencing unit in the executive boardroom.

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About the authors

Justin Fier

Justin Fier is the Director for Cyber Intelligence & Analytics at Darktrace, based in Washington D.C. Justin is one of the US’s leading cyber intelligence experts, and his insights have been widely reported in leading media outlets, including Wall Street Journal, CNN, the Washington Post, and VICELAND. With over 10 years of experience in cyber defense, Justin has supported various elements in the US intelligence community, holding mission-critical security roles with Lockheed Martin, Northrop Grumman Mission Systems and Abraxas. Justin is also a highly-skilled technical specialist, and works with Darktrace’s strategic global customers on threat analysis, defensive cyber operations, protecting IoT, and machine learning.

Dave Palmer

Dave Palmer is the Director of Technology at Darktrace, overseeing the mathematics and engineering teams and project strategies. With over ten years of experience at the forefront of government intelligence operations, Palmer has worked across UK intelligence agencies GCHQ & MI5, where he delivered mission-critical infrastructure services, including the replacement and security of entire global networks, the development of operational internet capabilities and the management of critical disaster recovery incidents. He holds a first-class degree in Computer Science and Software Engineering from the University of Birmingham.

Andrew Tsonchev

Andrew advises Darktrace’s strategic Fortune 500 customers on advanced threat detection, machine learning and autonomous response. He has a technical background in threat analysis and research, and holds a first-class degree in physics from Oxford University and a first-class degree in philosophy from King’s College London. He was most recently featured on BBC World, BBC Morning and Al Jazeera to comment on the news regarding the GRU.

Max Heinemeyer

Max is a cyber security expert with over eight years’ experience in the field specializing in network monitoring and offensive security. At Darktrace, Max works with strategic customers to help them investigate and respond to threats as well as overseeing the cyber security analyst team in the Cambridge UK headquarters. Prior to his current role, Max led the Threat and Vulnerability Management department for Hewlett-Packard in Central Europe. He was a member of the German Chaos Computer Club, working as a white hat hacker in penetration testing and red teaming engagements. Max holds a MSc from the University of Duisburg-Essen and a BSc from the Cooperative State University Stuttgart in International Business Information Systems.