Defensible Security Posture
June 4, 2013 21 Comments
Defensible Security Posture – Part 1
The purveyors of Fear, Uncertainty and Doubt (FUD) assert that preventing today’s advanced threats is unrealistic, internal compromise is inevitable and – that FUD factor is reinforced by more and more reports of malware and advanced attacks penetrating insufficient security controls. However, it’s not all doom and gloom. Although the experts concede that stopping 100% of attacks is a technical impossibility, there are ways for organizations to avoid becoming the next devastated victim.
Unfortunately ‘secure‘ is still the target of many CISOs and company leadership. From painful experience many security practitioners collectively know that ‘secure‘ is a mythical goal and doesn’t actually exist. The leap in logic proposed by this blog is that we move to something that’s ‘defensible‘.
The basic idea of a Defensible Security Posture is that you aren’t striving for an absolute, but rather for a position (or posture) that is able to be defended even when it’s infiltrated. The analogy that I like to use is the human immune system since security and advanced attacks are organic in nature and can come from various sources of infection. There are a few basic things we need to understand:
- Defensible does not mean secure
- There are more things to defend than there are resources to defend
- Sometimes your defenses can become your weakness
- Defensibility requires deep understanding of what critical assets you’re defending
- Defensibility focuses on what, why, how, when and from whom
Advanced Persistent Threats
The US National Institute of Standards and Technology (NIST) defines that an APT is:
An adversary that possesses sophisticated levels of expertise and significant resources which allow it to create opportunities to achieve its objectives by using multiple attack vectors (e.g., cyber, physical, and deception). These objectives typically include establishing and extending footholds within the information technology infrastructure of the targeted organizations for purposes of exfiltrating information, undermining or impeding critical aspects of a mission, program, or organization; or positioning itself to carry out these objectives in the future. The advanced persistent threat: (i) pursues its objectives repeatedly over an extended period of time; (ii) adapts to defenders’ efforts to resist it; and (iii) is determined to maintain the level of interaction needed to execute its objectives.
Attacks from APTs are growing in scope, increasing in frequency and, improving in effectiveness – to establish an insider base camp and cover tracks. Current strategies are not well-suited to mitigating prolonged and determined attackers leveraging a growing collection of stealthy techniques. The traditional perimeter and prevention response to threats is no longer realistic. Organizational resources need to shift the focus instead onto – Detection, Containment, Eradication and Recovery.
There is no silver bullet or single solution. Most organizations continue to focus on defending against zero-day exploits by relying on commercial security products to block bad sites and software and by patching systems to correct vulnerabilities in installed software. While these approaches are effective against some threats, they fail to stop the advanced attacks and provide no knowledge of what an adversary does once the network is penetrated.
APT attackers continually demonstrate their capability to compromise systems by using social engineering techniques, customized malware, and zero-day exploits that intrusion detection, anti-virus and patching cannot always detect or mitigate. Responses to APT intrusions require an evolution in analysis, process, visibility and technology. This blog describes an intelligence-driven, threat-focused approach.
Intelligence-driven Network Defense
Organizations may use a number of active techniques to detect attacks that can circumvent passive defenses. One approach uses honeypots to attract adversaries and look for patterns of behavior. Organizations may employ a number of active defense techniques within their own enterprises to detect and track adversaries as they explore networks. If a honeypot is set up with a number of different types of documents, organizations can watch to see which documents the adversary chooses to try to ex-filtrate.
Intelligence-driven Network Defense is a risk management strategy that addresses the threat component of risk, incorporating analysis of adversaries, their capabilities, objectives, doctrine and limitations. This is necessarily a continuous process, leveraging indicators to discover new activity. It requires a new understanding of the intrusions themselves, not as singular events, but rather as phased progression.
The benefit of Intelligence-driven Network Defense is a more resilient security posture. After all, APT attackers are persistent and attempt intrusion after intrusion, adjusting their operations based on the success or failure of each attempt. Once a compromise is achieved then the APT attacker deploys backdoors for contingency and covers any tracks.
The Signature of an APT
In any Advanced Persistent Threat (APT) attack there are typically a pre-defined set of phases that act as a signature, as follows:
The importance is not that this is a linear flow – some phases may occur in parallel, and the order of earlier phases can be interchanged – but rather how far along an adversary has progressed in his or her attack, the corresponding damage, and investigation that must be performed.
Reconnaissance – Research, identification and selection of targets, often represented as crawling Internet websites such as social networks, organizational conferences and mailing lists for email addresses, social relationships, or information on specific technologies.
Weaponization – Coupling a remote access trojan with an exploit into a deliverable payload. Increasingly, application data files such as PDFs or Microsoft Office documents serve as the weaponized deliverable.
Delivery – Transmission of the weapon to the targeted environment via, for example, email attachments, websites, and USB removable media.
Exploitation – After payload delivery to victim host, exploitation triggers intruders’ code. Exploitation targets an application or operating system vulnerability or leverages an operating system feature that auto-executes code.
Installation – Installation of a remote access trojan or backdoor on the victim system allows the adversary to maintain persistence inside the environment.
Command and Control – APT malware typically establishes remote command and control channels so that intruders have “hands on the keyboard” access inside the target environment.
Actions on Targets – Typically the prime objective is data exfiltration which involves collecting, encrypting and extracting information from the victim environment. Intruders may only seek access to victim box for use as a jump point to compromise additional systems and move laterally inside the network or attack other partner organizations.
Actionable Intelligence and the Intrusion Kill Chain
Cyber ‘kill chain’ methodology is the latest in a series of security strategies, targeted especially at APTs that are based on more of a proactive and visible model of real-time network monitoring, analysis, and mitigation. The formal concept of cyber ‘kill chain’ methodology was first developed by a group of scientists at Lockheed Martin in a paper titled, “Intelligence-Driven Computer Network Defense Informed by Analysis of Adversary Campaigns and Intrusion Kill Chains“.
The intrusion kill chain becomes a model for actionable intelligence where practitioners align organizational defensive capabilities to the specific processes an adversary undertakes to target that organization. The end goal of this is to analyze the data for patterns of attack methods, behaviors of distinct hostile actors, and other indicators which can inform the development of unique responses. Fundamentally, this approach is the essence of Intelligence-driven Network Defense security posture basing security decisions and measurements on a keen understanding of the adversary.
Defensible Actions Matrix
The following is an example of a table that depicts a course of action matrix using the actions of detect, deny, disrupt, degrade, deceive, and contain. Documenting the capabilities defenders can employ in this matrix as a tool enables the reader to assess their Defensible Security Posture as well as identify any gaps or needed compensating controls. The matrix includes traditional systems like network intrusion detection systems (NIDS) and Firewall access control lists (ACL), system hardening best practices like audit logging, but also vigilant users themselves who can detect suspicious activity.
Intelligence-driven Network Defense is a necessity in light of advanced persistent threats. As conventional, vulnerability-focused processes are insufficient, understanding the threat itself, its intent, capability, doctrine, and patterns of operation is required to establish resilience. The intrusion kill chain provides a structure to analyze intrusions, identify indicators and drive defensive courses of actions. This model prioritizes investment for capability gaps, and serves as a framework to measure the effectiveness of the defenders’ actions. When defenders consider the threat component of risk to build resilience against APTs, they can turn the persistence of these actors into a liability, decreasing the adversary’s likelihood of success with each intrusion attempt.
Evolving Towards a Defensive Posture
If your organization does not already have visibility with proactive monitoring built into your environment this may seem like a major challenge. Implementing an Intelligence-driven Network Defense with a Cyber Kill Chain should be based initially on a prototype then iterate approach to evolve in capability and sophistication. Start with a basic framework that you can comfortably build and operate then make progress from there.
Perform a Security Health Check with a focus on the organization’s web presence and external perimeter to see what information it could give an attacker – or leverage a 3rd party professional. Implement layered security to decrease the possibility that threats will slip through unnoticed. Create a policy for dealing with malware events. Educate staff about what to do with unexpected, suspicious emails and attachments.
With each step taken, you’ll get more information about your environment. And the more information you have, the more likely you will be able to identify anomalous behavior.
In Defensible Security Posture – Part 2 we discuss a case study that leverages the Defensible Actions Matrix and provides some recommended APT-focused best-practices.
The Defensible Security Posture series using an Intelligence-driven Network Defense will be built upon in future blogs. In the APT Operational Maturity and APT Intelligent Operations blogs we will discuss the need for a continuously evolving next-generation SIEM, risk management processes and, network behavior anomaly detection that enable organizations to take security operations and situational awareness to the next level, depending upon various factors including threat/risk profile.
The defensible architecture foundation uses Adaptive Zone Defense to segment critical assets from general-purpose infrastructure to enable containment that includes Application Architecture Taxonomy to discusses the analysis, placement, policy and, controls for assets based upon classification and risk. There will also be a blog that takes a deeper dive in Risk Management Practices.
Thanks for your interest!
Nige the Security Guy.