severity: The level of impact on a target environment caused by the activity (Required for Detection).description: Details the purpose of the query and any references (Required for Detection and Hunting).name: A short name of the detection in the form of a label (Required for Detection and Hunting).id: GUID (Required for Detection and Hunting).Trigger information: information for when the rule is triggered.Schedule: how often/when it should be run.Data Connectors: the data the rule should consider.Metadata: general information about the rule.I like to think of Sentinel Rules as structured into five parts: The Sentinel content repository also contains directories for each type of Rule which can be a good resource in comparing the two types ![]() However, the Hunting Query identifies system time changes, which can be indicative of malicious AND benign activity. You can see the Detection Rule is looking for an event that is clearly a security incident – security events should not be cleared. It uses Event Source Name “Microsoft-Windows-Eventlog” to avoid generating false positives from other sources, like AD FS servers for instance. Detection Rule: Security Event log cleared: Checks for event id 1102 which indicates the security event log was cleared.Event ID 4616 is only available when the full event collection is enabled. Hunting Rule: Windows System Time changed on hosts: Identifies when the system time was changed on a Windows host which can indicate potential timestomping activities.Let me illustrate using an example of each rule As a general rule of thumb, if Hunting Rules were made into Detection Rules there would be a lot of false positives. Hunting Rules will also typically require a human to interpret the results and decide on the next step based on the result. You can see the required properties needed for each type of Rule in the Query Style Guide. Hunting Rules do not have such properties because they are not triggered by time or by a condition – they are executed on-demand. Kind : scheduled queryFrequency : 1d queryPeriod : 1d triggerOperator : gt triggerThreshold : 0 The biggest difference between the two rule types is that Detection rules usually have time and threshold properties that can be defined to reduce noise on scheduled runs, e.g. Hunting Rules are designed to be run on-demand, typically during a hunt.īoth rule types are structured in YAML and most of the properties used by both rule types are the same. MCAS raising an alert) to identify security incidents. real-time) or when another event occurs (e.g. It is designed to be run on a schedule (inc. The two are very similar in structure, but it is important to understand the difference in there intended use.Ī Detection Rule is typically used for automated analysis. Microsoft Sentinel has two types of security content Hunting Rules and Detection Rules. If you are wondering where the name comes from, it’s named after Jacques Cousteau – a French undersea explorer – and you’ll see some cheeky references to Jacques in the Kusto documentation. Kusto was the original codename for the Azure Application Insights platform that Azure Monitor is now based on. ![]() Kusto Query Language is a simple and productive language for querying big data. ![]() Microsoft, who created the language, describe it as Unlike YARA-L which is specific to security events. The Kusto Query Language (KQL) is not unique to Sentinel, or security. It is first important to make the distinction in Sentinel between the Rule and the Query (sometimes you will hear the two terms used interchangeably). This tutorial will introduce the types of Sentinel Rules, how Kusto queries are written, and finally, how to convert a Kusto Query in Microsoft Sentinel into Sigma format. Given many organisations are still heavy Microsoft shops, it is not surprising. Microsoft Sentinel, whilst not exclusively a SIEM (it started life as a log aggregation platform), it is now beginning to compete well with other SIEM’s in the market that have grown from similar beginnings (Splunk, Elastic, etc.). In this post I will take a look at creating basic Kusto rules for Microsoft Sentinel (and show a manual conversion of a Sigma rule to Kusto rule).Ĭontinuing on from the last tutorial that examined Google’s YARA-L rule format, this week I will do the same with Kusto queries used by Microsoft Sentinel. Please view the post on for the full interactive viewing experience. If you are reading this blog post via a 3rd party source it is very likely that many parts of it will not render correctly.
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