Perform Threat hunting in Azure Sentinel

By Ashwin Venugopal -

 





CyberSecurity Threat Hunting

The term "threat hunting" is defined differently by different people. The most commonly used definition is that it is the idea that you are proactively hunting through your environment for a threat or a set of activities that you have not previously detected. 

Other uses of the term hunting includes searching for threats with newly obtained indicators. If a new IP Address considered harmful is provided by a Threat Intelligence Feed, an analyst can then note the IP address to search the log to find if the new indicator was seen in the past. Azure Sentinel already provides hunting queries to facilitate this process.Next, you can hunt for more evidence-based threats from a current Incident or Alert as part of an Incident Analysis Process which is vital to explore the data based on the evidence found in a current incident. Both Azure Sentinel and Microsoft 365 Defender provides this type of hunting capability.

Using KQL queries to find threats is the only thing common in all these approaches. Microsoft Defender and Microsoft Defender Endpoint are more focused on indicator and analysis type of hunting while Azure Sentinel provides more features to manage the threat hunting process.

Proactive hunts

Hunt should be done on the basis of a hypothesis which might start with "Operational Threat Intelligence", and then list the attackers' tactics and techniques. A hypothesis can search for a specific technique, not an indicator like an IP address and if a malicious activity is identified, we might have discovered the attacker earlier in the attack process before they have an opportunity to exfiltrate the data.

Process to hunt threats

Threat hunting is known as a continuous process and we can start at the top of our cycle with our hypothesis which helps us to plan out what we are going to hunt for, as well as requires us to understand where we are going to hunt and how we will do it. The hunting cycle doesn't stop when we execute hunt, there are still several phases we need to conduct throughout the life cycle, including responding to anomalies. Even if there is no active threat, there will always be activities to perform. Routine tasks should include:
  • Setting up new monitoring.
  • Improving our detection capabilities.  
Everything done in the threat hunting should be documented and it should include:
  • What, How, and Why
  • Input and Output
  • How to replicate the hunt
  • Next steps

Develop Threat Hunting Hypothesis

As we all know, Hunting should always start with a hypothesis i.e. the idea of what we are going to hunt and getting this right is critical because it drives our focuses on what we are going to do. There are many factors, but here are the key ones:
  • Keep it achievable- Don't perform a hunt where you know you have no hope of finding results because you don't have the data available or have insufficient knowledge about the threat to understand how to find it. 

  • Keep the scope narrow- Avoid broad a hypothesis such as "I am going to hunt for strange log-ons". Such a hypothesis fails to define what the results could mean.

  • Keep it time-bound- The time-bound is also used in documentation. If you time-bound your hunts there is a chance you will end up just repeating the same hunt on the same dataset. You will be able to say,"I did this hunt, at this time, covering this period". With this documented your team members will know what period was hunted for with this hypothesis.

  • Keep it useful & efficient- A good SOC team typically has a good idea about where their coverage is good and where it is weaker as well as needs improvement. There is no point in hunting fro an advanced threat that targets an industry you are not in or a platform you are not using.

  • Keep it related to the threat model that you are defending against- Otherwise, you may spend much time threat hunting for things that you will never find and which are not a threat.  

You should not start your Threat Hunting journey going after the most advanced threats, but you should start with the basics and incrementally mature your organization's Threat Hunting capabilities. You should always start with a simple Hunt Hypothesis and then gradually increase your capabilities.  








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