Triage

Threat Hunting at speed and scale

Almost every case starts with one or more leads. If there are too many leads, the investigator may need to validate each one individually, which is a time-consuming process. Alternatively, if there are too few leads, investigators lack sufficient information to continue their case. Neither situation is good for the investigation and can impact the speed of resolution.

Triage is the process of identifying and prioritizing the evidence that will be analyzed and evaluated. However, prioritizing this evidence is not a straightforward or easy job. An Investigator needs lots of data, leads, or experience to do it well. So, they generally use known attack indicators, referred to as the IOC (Indicator of Compromise). An indicator of compromise (IoC) in computer forensics is an artifact observed on a network or in an operating system that, with high confidence, indicates a computer intrusion.

An investigator or analyst will generally scan all system data or a portion of it to identify these IOCs. When they see a match, it typically means that those systems are related to a specific attack type and need to be investigated first. Investigators use YARA, osquery, and Sigma rules for these scans. Investigators can define and scan IOCs by using AIR's built-in YARA, osquery, and Sigma template rules or editors.

The AIR DFIR Suite provides investigators with three different tools for triage, which, as stated, are YARA, osquery, and Sigma. These tools generally scan assets to find specific data using IOC (Indicator of Compromise).

YARA (Yet Another Recursive Acronym) is a tool aimed at (but not limited to) helping malware researchers identify and classify malware samples. With YARA you can create descriptions of malware families (or whatever you want to describe) based on textual or binary patterns. Each description, a.k.a. rule, consists of a set of strings and a boolean expression that determines its logic.

Sigma is a generic and open signature format that allows you to describe relevant log events in a straightforward manner. The rule format is very flexible, easy to write, and applicable to any type of log file. The primary purpose of this project is to provide a structured form in which researchers or analysts can describe their developed detection methods and make them shareable with others. Sigma is to log files what Snort is to network traffic, and YARA is to files.

osquery, an open-source tool, employs SQL-like queries to extract intricate system data. It offers cross-platform compatibility, making it ideal for real-time system monitoring, security analysis, and compliance assessments. Security professionals often utilize it to detect vulnerabilities, monitor system changes, and ensure compliance with security standards.

AIR features a library for YARA, osquery, and Sigma rules, allowing investigators to develop, validate, and manage their rules directly within the platform using the built-in editors. These rules can be saved to Libraries > Triage Rules in AIR.

Investigators can efficiently conduct threat hunting and scan their assets by selecting the necessary rules from the library. The Triage process flow, depicted below, illustrates how organizational policies allow administrators to control AIR’s functionality and define role-based permissions for specific activities.

Creating a case in AIR also enables users to centralize all collections, triage results, and activities related to a specific incident or investigation. This integration allows the Investigation Hub to dynamically present all information, from raw evidence to automated DRONE findings, in a unified view.

Triage: Triage creation and execution flows

NB: Character limitation for a single triage rule

• To prevent the browser from becoming unresponsive, we have limited the maximum character count to 350K in a single Triage Rule.

Tagging Triage Rules

Triage rules in the AIR console can be assigned tags, which help organize the rules and filter them when required. This feature for triage rules enables more efficient management and allows for streamlined searches and improved organization within the console.

When creating or using a Triage Rule, the UI allows the user to filter existing rules by their associated Tags.

Triage: Tagging Triage Rules

The Triage Rule Library includes Preset Filters in the secondary menu, allowing users to organize rules hierarchically, also known as 'Nested Tagging'. By incorporating a colon in their tags, users can structure and categorize rules more efficiently. For example, the tag "APT26:Tim:hashset" helps organize related rules under a structured hierarchy, enhancing navigation and accessibility in the library.

Scan Local Drives Only for Triage Tasks

With the Scan Local Drives Only feature, users can improve Yara triage efficiency by focusing threat hunting and triage scans solely on local drives, excluding remote external or network drives that often introduce unnecessary data into the investigation. The attached mounted USB drives should be included as ‘local drives’.

Key Details:

• Available for all AIR-supported operating systems.

• Disabled by default, but can be toggled on or off via Settings > Policies > New Policies > Scan Local Drives Only. This setting can also be modified later.

• It can also be configured during the customization step when creating triage tasks via 'Use Custom Options'.

Triage: Custom option to scan local drives only

This feature ensures that only relevant data from local drives is collected, reducing noise and improving the speed and accuracy of investigations.