What is DFIR?
Digital Forensics and Incident Response Explained
Digital evidence is often involved in crimes, and every serious security incident or data breach requires a post-mortem investigation that only DFIR personnel can provide.
In this 101, we’re going to cover:
What is DFIR (Digital Forensics and Incident Response)?
DFIR (Digital Forensics and Incident Response) is a highly specialized sub-field of cybersecurity that focuses on identifying, remediating, and investigating cyber security incidents.
DFIR is a combined discipline, bringing together two slightly separate skill sets to achieve the desired outcome.
DF (Digital Forensics)
Whenever a crime scene is digital or includes digital evidence, forensic techniques are implemented to capture and preserve evidence. This evidence comes from file systems, the operating system, and other sources, and produces a detailed view of cyber activity.
Only through digital forensics can a chain of custody be created that is accurate enough to be admissible by law enforcement and court proceedings. Forensic investigations are “low and slow” in nature, not concerned with speed but rather accuracy and getting to the truth.
Common forensic data sources and artifacts include:
- Full disc images
- Memory forensics
- File system forensics
- Network Forensics
IR (Incident Response)
Incident Response is a complementary process that focuses on cyber intrusion, hacking, and insider threats, and evidence is not necessarily expected to be admitted in court or used by law enforcement. Digital forensic techniques are useful to investigate, while the practice of Incident Response exists to remediate and recover. These are separate but related in the event of post-mortem investigations and data breaches to return impacted systems to a safe, trusted, and uncorrupted state by threat actors. Deep dive incident response is a path to permanent remediation, whereas at times a fast-moving EDR may only produce partial remediation.
After a serious security incident, IR techniques help to close gaps in security coverage and avoid repeat incidents of the same type in the future. Lessons learned from the investigative process can reveal gaps in security coverage that led to a data breach, and these gaps can be closed through endpoint hardening, vulnerability management, patching, and other methods.
IR focuses more on speed to resolution. The first 72 hours are critical to understanding the full scope and impact of a threat actor's actions in the environment.
DF + IR
Although separate, these are related fields and when combined the outcome is powerful. DFIR is useful to answer questions like:
- Who attacked? (Attribution)
- What is the full scope and impact of the incident?
- How did the attacker get in?
- What steps were taken to escalate the operation?
- How do we ensure this type of attack won’t occur again?
- How do we fully remediate the existing issue to restore trust?
DFIR can also be useful to reverse engineer and analyze malware. What is a particular binary or script programmed to do when activated?
With the onslaught of sophisticated attacks and frequent data breaches, DFIR is increasingly a valued part of a successful defense strategy.
The Value of DFIR
DFIR is highly relevant in the modern threat landscape. Digital evidence is often involved in crimes, and every serious security incident or data breach requires a post-mortem investigation that only DFIR personnel can provide.
Every digital interaction leaves traces that can be examined after the fact. If the interaction was part of a cyber compromise or criminal activity, DFIR is needed to fully understand the situation.
DFIR Components Include:
- Examination of forensic evidence
- Deep dive investigation
- Post-mortem analysis of security events
- Breach response and recovery
- Evidence preservation
Mature organizations with a SOC and Tier III expertise in-house are more likely to have DFIR capabilities on hand, while less mature organizations rely on outside services to benefit from DFIR investigations and outcomes.
DFIR Process
According to the National Institute of Standards and Technology (NIST), the IR Lifecycle includes the following steps:
- Preparation. DFIR teams should have a plan that includes detailed actions that would account for a wide range of incidents. This plan should be prepared in advance, thoroughly understood by team members, and regularly adjusted to incorporate new threats and threat vectors.
- Detection and Analysis. The situation must be understood fully to ensure an appropriate response. Teams will need to collect evidence, and analyze forensic artifacts and full disc images, memory artifacts, file system artifacts, and other sources to aggregate all necessary evidence. Once the evidence has been gathered, a timeline should be built that incorporates root cause, patient zero, and all steps taken by adversaries while in the environment
- Containment, Eradication, and Recovery. Once the situation is fully understood, the threat should be contained and remediated. Forensic remediation should lead to permanent remediation of the encountered threat and should incorporate all aspects of the compromise.
- Post Incident Activity. Post-mortem, DFIR teams should incorporate lessons learned to shore up gaps in defenses. It may also be necessary to retain evidence for a period of time.
DFIR Team
Tier III IR practitioners and Forensic Examiners often conduct DFIR. These individuals sit within a SOC and work closely with the CISO, SOC Manager, Privacy Officer, Legal teams, and other SOC analysts.
DFIR Toolkit
The DFIR toolkit is more essential than ever given the proliferation of cyber attacks and data breaches. DFIR processes are often undocumented and practitioners gain their skillset through informal sharing of unwritten knowledge.
The most valuable tool any DFIR practitioner has at their disposal is their brain. Like a detective, a successful investigation is primarily driven by instinct and knowledge gained from past experience. DFIR tools are only as good as their operators — DFIR takes experts.
Still, there are many tools needed for standard investigations. The types of deep-dive investigations DFIR practitioners undertake require the ability to collect, splice, and analyze evidence. DFIR personnel often rely on both open-source and licensed tools, with potentially dozens of tools involved in a single investigation. DFIR tools should work well with an EDR solution and where possible investigation results should be centralized.