What is digital forensics and incident response (DFIR)?

DFIR integrates two discrete cybersecurity disciplines: Digital forensics, the investigation of cyberthreats, primarily to gather digital evidence for litigating cybercriminals; and incident response, the detection and mitigation of cyberattacks in progress. Combining these two disciplines helps security teams stop threats faster, while preserving evidence that might otherwise be lost in the urgency of threat mitigation.

Digital forensic experts investigate and reconstruct cybersecurity incidents by collecting, analyzing and preserving digital evidence—traces left behind by threat actors, such as malware files and malicious scripts. These reconstructions allow experts to pinpoint the root causes of attacks and identify the culprits.

Digital forensic investigations follow a strict chain of custody or formal process for tracking how evidence is gathered and handled. The chain of custody allows investigators to prove that evidence wasn’t tampered with. As a result, evidence from digital forensics investigations can be used for official purposes like court cases, insurance claims, and regulatory audits.

The National Institute of Standards and Technology (NIST)  outlines four steps for digital forensic investigations:

Incident response focuses on detecting and responding to security breaches. The goal of incident response is to prevent attacks before they happen and to minimize the cost and business disruption of attacks that occur.

Incident response efforts are guided by incident response plans (IRP), which outline how the incident response team should deal with cyberthreats. The incident response process has six standard steps:

1. Preparation: Preparation is the ongoing process of assessing risks, identifying and remediating vulnerabilities (vulnerability management) and drafting IRPs for different cyberthreats.
   
   
2. Detection and analysis: Incident responders monitor the network for suspicious activity. They analyze data, filter out false positives and triage alerts.
   
   
3. Containment: When a breach has been detected, the incident response team takes steps to stop the threat from spreading through the network.
   
   
4. Eradication: Once the threat has been contained, incident responders remove it from the network—for example, by destroying ransomware files or booting a threat actor from a device.
   
   
5. Recovery: Once incident responders have removed all traces of the threat, they restore damaged systems to normal operations.
   
   
6. Post-incident review: Incident responders review the breach to understand how it happened and prepare for future threats. 

When digital forensics and incident response are conducted separately, they can interfere with one another. Incident responders can alter or destroy evidence while removing a threat from the network, and forensic investigators may delay threat resolution as they search for evidence. Information may not flow between these teams, making everyone less efficient than they could be.

DFIR fuses these two disciplines into a single process carried out by one team. This yields two important advantages:

Forensic data collection happens alongside threat mitigation. During the DFIR process, incident responders use forensic techniques to collect and preserve digital evidence while they’re containing and eradicating a threat. This ensures that the chain of custody is followed and valuable evidence isn’t altered or destroyed by incident response efforts.

Post-incident review includes examination of digital evidence. DFIR uses digital evidence to dive deeper into security incidents. DFIR teams examine and analyze the evidence they’ve gathered to reconstruct the incident from start to finish. The DFIR process ends with a report detailing what happened, how it happened, the full extent of the damage and how similar attacks can be avoided in the future.

Resulting benefits include:

• More effective threat prevention. DFIR teams investigate incidents more thoroughly than traditional incident response teams do. DFIR investigations can help security teams better understand cyberthreats, create more effective incident response playbooks and stop more attacks before they happen. DFIR investigations can also help streamline threat hunting by uncovering evidence of unknown active threats.
  
  
• Little or no evidence is lost during threat resolution. In a standard incident response process, incident responders may err in the rush to contain the threat. For example, if responders shut down an infected device to contain the spread of a threat, any evidence that is left in the device’s RAM will be lost. Trained in both digital forensics and incident response, DFIR teams are skilled at preserving evidence while resolving incidents.
  
  
• Improved litigation support. DFIR teams follow the chain of custody, which means the results of DFIR investigations can be shared with law enforcement and used to prosecute cybercriminals. DFIR investigations can also support insurance claims and post-breach regulatory audits.
  
  
• Faster, more robust threat recovery. Because forensic investigations are more robust than standard incident response investigations, DFIR teams may uncover hidden malware or system damage that would have otherwise gone overlooked. This helps security teams eradicate threats and recover from attacks more thoroughly.

In some companies, an in-house computer security incident response team (CSIRT), sometimes called a computer emergency response team (CERT), handles DFIR. CSIRT members may include the chief information security officer (CISO), security operations center (SOC) and IT staff, executive leaders and other stakeholders from across the company.

Many companies lack the resources to carry out DFIR on their own. In that case, they may hire third-party DFIR services that work on retainer.

Both in-house and third-party DFIR experts use the same DFIR tools to detect, investigate and resolve threats. These include:

• Security information and event management (SIEM): SIEM collects and correlates security event data from security tools and other devices on the network.

• Security orchestration, automation, and response (SOAR): SOAR enables DFIR teams to collect and analyze security data, define incident response workflows and automate repetitive or low-level security tasks.

• Endpoint detection and response (EDR): EDR integrates endpoint security tools and uses real-time analytics and AI-driven automation to protect organizations against cyberthreats that get past antivirus software and other traditional endpoint security technologies.

• Extended detection and response (XDR): XDR is an open cybersecurity architecture that integrates security tools and unifies security operations across all security layers—users, endpoints, email, applications, networks, cloud workloads and data. By eliminating visibility gaps between tools, XDR helps security teams to detect and resolve threats faster and more efficiently, limiting the damage that they cause.