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AndrewMundell

Introduction

Welcome to the Sophos EDR Threat Hunting Framework. This document is intended to guide an experienced threat hunter through the process of initiating a hunt, gathering and enriching data, then taking the required action using Sophos EDR tools (Live Discover, Live Response, and Clean & Block).

At the time of publishing, this guide is focused on the Microsoft Windows Operating Systems, additions for macOS and Linux are coming soon.

Sophos EDR Threat Hunting Foundations

Sophos EDR is a toolset that enables human threat hunters to quickly discover signals, assess the context of those signals and perform the necessary actions to remediate a discovered threat or to refine the threat hunting process to rule out "false positives" in future hunts. The glossary below will familiarize you with the Sophos terminology used throughout this guide.

Term Sophos EDR definition
Live Discover Live Discover is the Sophos EDR feature that enables a threat hunter to query and retrieve data from the targeted devices
Live Discover query A query is a mechanism of defining what data should be retrieved from the targeted devices, Sophos uses the Osquery engine which uses SQLite syntax queries
Osquery A framework that processes SQL language queries and allows data sets on the device (e.g. Event viewer, registry, system properties) to be seen as database tables for data extraction and filtering. You can view the native Osquery schema at Osquery Schema v4.2.0
Sophos journals Sophos forensic journals containing up to 90 days of data of process, file, registry key and network connection data. Sophos has extended Osquery to provide access to these journals as tables that can be queried. You can view the schema of these journals at Live Discover Schema
"Signal" In this guide, we'll use the word "signal" to describe a discrete item that requires further investigation, e.g. a process that created a file that is considered an Indicator of Compromise (IOC)



Examples of possible "signals" discoverable		 Sophos PID An identifier for a single unique execution of a process
Sophos ML score 1-100, higher is more likely malicious
Sophos local reputation The SophosLabs reputation of the file as cached on the targeted device
Sophos global reputation If looked up via Sophos Live Protection, this is the reputation score as classified at the time of lookup by SophosLabs
Sophos PUA score 1-100, lower is more likely PUA
Live Response Live Response is the Sophos EDR feature that enables a threat hunter to interact with a targeted device remotely in a SYSTEM/ROOT level command prompt
Device isolation Device isolation is the Sophos EDR feature that enables a threat hunter to isolate a targeted device from the network, whilst still allowing management communications to Sophos Central and customer defined exclusions for local remote access. You can read more about customer defined exclusions at Device isolation exclusions (Windows)

Threat Hunting Process

Sophos threat hunters use the process below when initiating and running through a threat hunt. In this guide, we'll break down each section of this process into the steps in the Sophos EDR toolset which help hunters perform their initial hunts, gather the required contextual data from the targeted devices and 3rd party sources, and take the necessary actions to neutralize a detected threat or refine the hypothesis to reduce "false positive" signal detections.

Propose Hypothesis

This section will guide you through defining your threat hunt hypothesis in Sophos EDR. There are 4 types of hypothesis that this guide will cover:

  1. Identifying the presence of Indicators of Compromise (IoC) - Use Threat Search or Live Discover to identify the presence of IOCs and triage the results using Threat Cases or further Live Discover Queries
  2. Sophos provided Live Discover queries - Sophos provides a number of pre-built queries for threat hunting and IT hygiene, we'll highlight some of the most useful ones in this section
  3. EDR Community published queries - Sophos staff, customers and partners publish interesting queries to a curated forum hosted by Sophos
  4. Defining your own custom query to match your hypothesis - The in-depth data available in the Sophos Journals enables a threat hunter to define their own queries to evaluate and investigate hypotheses

Presence of Indicators of Compromise (IoC) via Threat Searches
Searching for a threat Next steps

You can use the Threat Searches section of the Threat Analysis Center to quickly search for one or more file names, SHA-256 file hashes, IP addresses, domains or command lines.

Searches find PE files (like applications) with uncertain or bad reputations and network destinations they've connected to.

Searches also find activity by admin tools, which can be used maliciously.

Threat Searches

If a Threat Search identifies the presence of an IOC you can create a simple Threat Case to investigate and gather signals for further Live Discover queries in the Aquire & Analyze data section.

If you are sure that the searched for PE is malicious and is not being proactively blocked by the Sophos agent, you can "Clean and Block" to remove it from systems and add it to a global block list.

Presence of Indicators of Compromise (IoC) via Live Discover
Source of IOCs Query to discover signals Query input Query output Next steps
Lists of IOCs in CSV format

Sophos has published a query that can process a list of IOCs in a CSV format.

Visit the link below for the details of the variables needed, and the query itself.

Sophos Cybersecurity GitHub page for generic IOC threat hunt query

SophosLabs publishes IOCs in this format :

SophosLabs IoCs

NOTE: Use the "raw" URL from GitHub, e.g. for Conti Ransomware:

https://raw.githubusercontent.com/sophoslabs/IoCs/master/Ransomware-Conti.csv

We expect other CSVs using the same format to be properly processed by the same query.
  • Date & time
  • IOC Type (defined in CSV)
  • indicator
  • Note (defined in CSV)
  • Subject (e.g. files, registry keys, network connections)
  • Sophos PID
  • Process name
  • Action performed by/to the IOC
  • Activity involving the IOC (object)
 Use the queries in the "Acquire and analyze data" section to investigate any Sophos PIDs, files and/or Registry keys of interest
Individual IOCs

Threat Hunting > Processes matching SHA-256 hashes in the last 30 days
  • Process SHA-256 hash
  • SHA-256
  • path
  • Sophos PID
Network > IP address activity
  • Start time
  • End time
  • IP address
  • Date & time of connection
  • Sophos PID
  • Process name
  • Source IP / port
  • Destination IP / port
  • Protocol
Files >File access history
  • Start time
  • End time
  • File path (use % wildcard at the beginning of file name to search in all folders)
  • Date & time of activity
  • Process
  • Event type
  • File name
  • Process path
  • File path
  • Sophos PID
  • SHA-256 of process

Sophos Live Discover is available for automation/bulk processing of queries via the Sophos Central API. Full details are online at the documentation site below:

Live Discover API at Sophos API Developer site

Leveraging a built-in Live Discover query
Behavior identified Category > Name of query Query input Query output Next steps

Lists all remote authentication attempts (requires Windows event audit logging)

ATT&CK > Remote Authentication Attempts

None
  • Date & time of attempt
  • Domain
  • Username
  • Remote address
  • Logon type
  • Logon result
 Triage any unexpected logins, especially from non-LAN IP ranges
Identifies unsigned applications that were run on the device on the last day. Code signing shows this is an authentic binary from the developer and has not been tampered with. (Code signing MITRE ID T1116) ATT&CK > Unsigned applications that were run None
  • Date & time of execution
  • Process path
  • Sophos PID
  • Process SHA-256
  • Sophos Global reputation
  • Sophos Local reputation
  • Sophos ML score
 Use the process queries in the "Acquire and analyze data" section to investigate any unsigned processes and perform the necessary response actions
Lists unquoted paths in the service registry keys. Unquoted paths allow an adversary to place an application in a higher-level directory so that Windows finds that application instead of the intended one. (MITRE category T1034) ATT&CK > Unquoted paths in the service registry keys None
  • Registry key path
  • Registry key data
 Use the registry key queries in the "Acquire and analyze data" section to understand what process generated the key in question and triage other discovered signals as necessary
Lists processes that have a Remote Desktop (RDP) connection to an external device

Network > Devices that have a Remote Desktop connection

 None
  • Connection type
  • Remote address & port
  • Local port
  • Sophos PID

Triage any unexpected logins

NOTE: The query removes connections on local subnet ranges
Lists all processes that scheduled tasks and their details. Requires Windows audit object access logging

Processes > Processes that scheduled tasks
  • Start time
  • End time
    (of the creation of the scheduled task to search for)
  • Date & time of creation
  • Sophos PID
  • Process name
  • Command line
  • Parent process Sophos PID
  • Parent proces name

 Use the process queries in the "Acquire and analyze data" section to investigate the process that created the scheduled task and triage other discovered signals as necessary
NOTE: Sophos regularly adds new generic signal discovery queries, check the "Last modified" column on the list of all queries to see the latest additions

Using a Sophos EDR Community published query + 3rd party queries
Query description and URL Query input Query output Next steps

Sophos curates a collection of community posted queries contributed by Sophos staff, partners and customers. Visit the Live Discover & Response Query Forum at this link to participate!

Below are two particularly useful queries for detecting the use of encoded PowerShell and gathering data based on a number of variables. To use these, or any other queries available in the Community, follow these steps to create a custom query:

  1. At the Sophos Central Dashboard, navigate to "Threat Analysis Center" > "Live Discover"
  2. Click the "Create new query" button
  3. Choose a name for the query, select one or multiple categories
  4. Optionally add a description
  5. Choose the Operating Systems to which the query will apply
  6. Expand the variable editor and click "+ Add variable" to create a variable
  7. Enter the descriptive name, select the variable type
  8. The SQL variable name will be populated automatically
  9. Enter an initial value for the variable
  10. In the "SQL" box, enter the SQL code for the query
  11. Click the "Save" button

Identification of the use of encoded PowerShell commands

Decode encoded powershell query at the Sophos Community
  • Return 
  • From N days ago
  • To N days ago
  • Date & time of execution
  • Original command line
  • Sophos PID
  • Decoded command line
  • Parent process Sophos PID
  • Use the Sophos PID to run a process tree to see what caused the PowerShell to execute

Generic search for activity gathering

Generic search query at the Sophos Community

NOTE: you don't have to fill in every variable

Example uses:

  1. Identify rare behavior of one specified process being spawned by another
    1. Use process name and parent process name variables
  2. Identify clicked links
    1. Use "http%" in the command line variable
    2. Use a specific URL in the command line variable
  3. Identify all activities carried out by the specific user in the specified time frame
    1. Use the user name in the user name variable
  • Date to start search from
  • Command line to search
  • Date to end search on
  • Process name to search
  • Parent process name to search
  • User name to search
  • Date and time of activity
  • User name
  • Parent process name
  • Process name
  • Command line
  • Visualization of execution duration
  • Sophos PID
  • Parent Sophos PID
  • Use the process queries in the "Acquire and analyze data" section to investigate any discovered processes
NOTE: Sophos Live Discover is built on the foundation of Osquery, an open-source framework. We expect queries written by 3rd parties and using the same Osquery schema to work unmodified in Sophos Live Discover.

Creating a custom query for a behaviour not yet covered by a built-in or Community query

You can create your own custom query using the steps below, these queries are available to all administrators and can contain variables for simple reuse.

  1. At the Sophos Central Dashboard, navigate to "Threat Analysis Center" > "Live Discover"
  2. Click the "Create new query" button
  3. Choose a name for the query, select one or multiple categories
  4. Optionally add a description
  5. Choose the Operating Systems to which the query will apply
  6. Expand the variable editor and click "+ Add variable" to create a variable
  7. Enter the descriptive name, select the variable type
  8. The SQL variable name will be populated automatically
  9. Enter an initial value for the variable
  10. In the "SQL" box, enter the SQL code for the query
  11. Click the "Save" button

In the sections below we'll outline some important things to know about creating your own queries. This isn't an exhaustive list of Osquery / SQLite resources, if you're having problems with a particular query we recommend reaching out to the Live Discover & Response Query Forum for assistance.

Schema

Review the core Osquery Schema v4.2.0 schema and the extensions added by Sophos to the Live Discover Schema to funny understand the capabilities and the data that's available to retrieve

Variables

Live Discover queries support variables, review the Edit or create a query section of the online documentation for full details.

NOTE: Variables names cannot contain the dollar sign ($) character

NOTE: Reference variables in your custom query by calling the "Descriptive name" field surrounded by "$$", e.g. for a query with a Descriptive name of "File name" use "$$File name$$" in the query

Wildcards & operators

Live Discover queries support SQLite wildcards and operators, below is a list of the most frequent wildcards and operators you might want to use in a query:

  • = [Equal to]
  • != [Not equal to]
  • < [Less than]
  • > [Greater than]
  • % [Match 0 or more wildcards]
  • _ [Match exactly 1 wildcard]
  • WHERE [applies a filter to the results]
  • AND [applies multiple filters to the results and matches all]
  • LIKE & NOT LIKE [matches or doesn't match a pattern with a wildcard modifier]
  • JOIN [link results across multiple tables]
  • IN ('x', 'y', 'z') [matches one or more of the bracketed contents, use instead of "OR"]

You can read more detailed documentation about SQL As Understood By SQLite online.

Query limitations

Both endpoint/server devices and Sophos Central have guardrails to prevent a query from causing undesired behavior.

Below is an extract from the Live Discover Overview article:

  • Endpoint/Server devices:
    • Watchdog: Devices have a watchdog that will terminate a query if it exceeds 30% of the device's available CPU for 12 seconds or exceeds 256MB of memory.
    • Return Data Size Limit: Each device is limited to 10MB of data for the response to any single query.
    • Single Row of data size limit: the device is further restricted to a maximum of 1MB of data for a single row.

      NOTE: If this condition is detected, the query will appear to return data, but nothing will be presented in Sophos Central. It is possible to hit this limit when looking for the content of a PowerShell event or registry key.

  • Sophos Central:
    • Sophos Central will limit the total number of rows from all responding devices to 100K rows of data. Once this limit is reached, Sophos Central will drop additional data returned and inform the devices still processing a query to not return data.

Acquire and Analyze Data

In this step, we acquire more data about the signal identified by our initial query. Throughout this stage, we'll identify further signals which will each need investigating and triaging to generate a complete picture of the series of events before and after the generation of the initial signal. Loop through the appropriate queries for each signal acquired until we fully understand all of the steps leading to the initial presence of the discovered signal, and any subsequent actions taken by or it or adjacent processes or files.

For complex query results, the data can be exported as a CSV file for further analysis or filtering in your preferred tool.

PROCESS
Built-in queries Query input Query output Suggested next steps

Processes > Process details for a Sophos PID
  • Sophos PID
  • path
  • command-line parameters passed on launch
  • Sophos ML malware & PUA scores
  • SHA-256 hash
  • start time
  • end time
  • Use 3rd party intel to confirm the provenance of the process via SHA-256 lookup
  • Identify if command line parameters are suspicious
  • Use the start/end times to narrow subsequent queries (e.g. file or registry) 

Processes > Process Tree for Sophos PID
  • Sophos PID
  • parent & child processes
  • command line parameters passed on launch for each process
  • Identify further process executions which require investigation
  • Use 3rd party intel to confirm the provenance of additional processes via SHA-256 lookup

Processes > Process activity history
  • Sophos PID
  • start time
  • event category (subject)
    • e.g. files, registry keys, network connections
  • event type (action)
    • e.g. read, deleted, connection made
  • item which was effected (object)
    • e.g. file path, registry key name, destination IP and port

Full details of the subject, action and object field contents are available in the sophos_process_activity table on the Live Discover Schema.
  • Triage the data returned to fully understand the activities of the investigated process during its entire recorded execution
  • Identify any files, registry key or network connections which are of interest and triage those items using the appropriate query

FILE
Built-in queries Query input Query output Suggested next steps
Files > File attributes and metadata
  • File path
  • Path
  • User ID (UID) of the owning user
  • File size
  • Last access time (atime)
  • Last modification time (mtime)
  • Last status change time (ctime)
  • Creation time (btime)
  • Use the creation time (btime) value to refine the "Files > File access history" query to identify the process that created the file

Files > File access history
  • Start time
  • End time
  • File path
  • Time of the activity
  • Event type
    • e.g. created, accessed, deleted
  • For the process that carried out the activity
    • name
    • path
    • Sophos PID
    • Sophos ML malware & PUA scores
    • SHA-256 hash
  • Use the Sophos PID value in the process queries section of this guide to gather data about the creating process
  • Identify further processes which interacted with this file that may need to be investigated

Files > File hashes
  • File path
  • MD5 hash
  • SHA-1 hash
  • SHA-256 hash
  • Use the hashes returned to enrich context from 3rd party threat intel providers

REGISTRY KEY
Built-in queries Query input Query output Suggested next steps
Registry > Display registry section
  • Registry key name

NOTE: add "/%" to the end of the desired registry key to retrieve the full content
  • Registry key
  • Registry key value (valueName)
  • Type of value (valueType)
  • Registry key value data (valueData)
  • Last modified time (lastTimeModified)
  • Use the last modified time (lastTimeModified) value to refine the "Registry > Processes that modified a registry key" query to identify the process that modified the key
  • Consider if the Registry key value and value data may contain useful intelligence and should be further enriched
Registry > Processes that modified a registry key
  • Start time
  • End time
  • Registry key name
  • Date & time of change
  • Sophos PID
  • Process name
  • Event type
  • Registry key
  • Registry key value (valueName)
  • Registry key value data (value)
  • Use the Sophos PID value in the process queries section of this guide to gather data about the modifying process.
  • Consider if the Registry key value and value data may contain useful intelligence and should be further enriched

Device Isolation

As you loop through the data acquisition queries, you might find yourself becoming more convinced that there are potentially harmful activities happening on one or more devices. You can use device isolation at any time to restrict those devices connection to both local and remote networks. Devices will still be able to communicate with Sophos Centra and you can define your own exclusions for local devices to connect remotely to assist in the investigation.

Inform and Enrich

In this section we'll cover the next stage of threat hunting, which is to gather further information about the signals we discovered in the previous loops through the data acquisition queries. Typically we're looking to confirm if other intel sources believe the signal to be malicious or benign, identify if an IP address is hosting a Command and Control server or decode encoded strings discovered in command lines.

NOTE: We recommend using as many data sources as possible before concluding that a detection may be a false positive to avoid any bias from a single source.

Examples of resources that can provide enrichment for discovered signals, please note that some of these resources are 3rd parties and are not affiliated with Sophos, and Sophos has no control over the content you may see on these sites.

Service

Items that can be looked up
Items that can be analyzed
More info at...
SophosLabs Intellix
  • SHA-256 file hash
  • URL category & reputation
  • IP category & reputation
  • Android APK
  • Static file
  • Dynamic file
  • Static URL

SophosLabs Intelix

Static analysis of PE files is available via Sophos Central. Review the Threat Case examples (Malware detections) documentation for further details.
Virus Total
  • URL
  • IP address
  • domain
  • file hash
  • Static file
  • Static URL

https://www.virustotal.com

VirusTotal was founded in 2004 as a free service that analyzes files and URLs for viruses, worms, trojans and other kinds of malicious content.
Shodan
  • IP address

https://www.shodan.io

Shodan is a search engine that lets the user find specific types of computers (webcams, routers, servers, etc.) connected to the internet using a variety of filters.
CyberChef
  • Encoded content to be decoded

https://gchq.github.io/CyberChef

CyberChef provides a simple "recipe" based platform for decoding obfuscated strings typically found in command lines for processes like PowerShell

Act

In this final stage of our threat hunt, we've used threat intel to determine if we need to act to contain a threat, or if we should refine our threat hunt hypothesis or subsequent queries to better remove false-positive signals.

ACT
Enhance detections to reduce FPs Valid threat

You can create copies and then edit any of the built-in queries, and edit manually added queries directly in Sophos Central.

Consider adding SQL filters to queries to reduce the number of initial signals identified and increase the likelihood that further signals will not be "false positives".

 Portable Executable

If you've identified a valid threat in the form of a portable executable, you'll first want to block the file by its SHA-256 hash. Follow the instructions in the documentation for Blocked items. Adding a SHA-256 hash to the blocked items list removes any files matching the hash on all machines, and it proactively blocked on all other machines.

If the detection was not in a folder or file which was specified in a Global exclusion or Policy based exclusion, we request that you submit a sample of the file to SophosLabs. If the detection was in a folder or file which was excluded, consider changing or removing the exclusion.
IP or URL

If you've identified a valid threat in the form of a malicious IP address or URL, you'll want to block communications to that item in as many places as possible.

You can use Sophos Web Control to block access to a URL, domain, IP address or CIDR range, make sure to create the "site" in Website Management in Global Settings, then add to both Endpoint and Server Web Control policies.

You should also block access at your network firewall, proxy server, web gateway etc...
Other mitigations

Using Live Response - Live Response is a remote terminal connection enabling the investigator to perform any action that can be carried out via the terminal, this includes launching other shells, such as PowerShell on Windows.

NOTE: Live Response is disabled by default, and has separate settings for endpoints and servers. Once enabled for both device types, only Super Admin role administrators can use Live Discover. You can use custom roles to delegate Live Response permissions to non Super Admin roles. Administrators must be logged in using MFA to use Live Response.

Documentation is online for the steps to set up and start Live Response and how to add a custom role if needed.
Compromised account detected - If you've concluded that a user or admin account has been compromised you should disable the account immediately. We recommend requiring MFA for all services that offer it. Follow these steps to check your Sophos Central MFA settings.

Summary

Thank you for reviewing the Sophos EDR Threat Hunting Framework. Check back often as we'll expand this guide to cover more operating systems and feature additional built-in and community posted queries.

NOTE: If you believe you are under active attack, the Sophos Rapid Response service is available to perform containment and remediation steps.

The Sophos Managed Threat Response service can act as your 24/7 threat hunting and response team and can be added to any Endpoint or Server protection license that's managed in Sophos Central.

Finally, below are some great resources for getting started with Sophos EDR:

Resource type Location

Sophos Blog articles related to threat hunting
Sophos Live Discover technical resources
Sophos EDR threat hunting in action

Parents

  • Hi Andrew

    Thank you for this, and the session today.

    Can I just ask the following please:

    • ATT&CK > Unquoted paths in the service registry keys - I've just tested this and it lists the path "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\hmpalertsvc\ImagePath" with the data "C:\Program Files (x86)\HitmanPro.Alert\hmpalert.exe /service". I believe this is Sophos software?
    • The built-in Live Discover query ATT&CK > Remote Authentication Attempts doesn't appear to be available to me.

    Thanks again!

  • in reply to S1P

    Hi there, good spot on the unquoted paths, that Is part of Intercept X and I hear an update that'll be rolled out shortly will take that out of the results.

    I'll have to look into the remote authentication attempts query and I'll get back to you shortly.

    Thanks for getting in touch!
    Andrew

Comment
  • in reply to S1P

    Hi there, good spot on the unquoted paths, that Is part of Intercept X and I hear an update that'll be rolled out shortly will take that out of the results.

    I'll have to look into the remote authentication attempts query and I'll get back to you shortly.

    Thanks for getting in touch!
    Andrew

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