Best practices provide guidelines to help you write and manage rules, deploy rules, and maintain system health for your ESA services.
Understand Event Stream Analysis Rule Types
The ESA Correlation service provides advanced stream analytics such as correlation and complex event processing at high throughputs and low latency. It is capable of processing large volumes of disparate event data from Concentrators. However, when working with Event Stream Analysis, you should be aware of the factors that affect resource usage in order to create effective rules.
Each event that is received by ESA is evaluated to determine if it may trigger a rule. There are three types of rules that can be deployed in order to determine what the ESA engine should do with the incoming event. Each of these rule types have different impacts on system resource utilization. All three rule types may be created via the Rule Builder, Advanced Event Processing Language (EPL) rules, or downloaded via RSA Live. The table below lists the rule type and the impact this rule may have on system resources.
Simple Filter Rule
This rule has no correlation to other events. At ingestion time, this rule is evaluated against a set of conditions, and if those conditions are met an alert is generated. If no conditions match, the event is quickly released by the engine to free up memory usage. These rules do not take up memory since the events are not retained beyond the initial evaluation. The memory resource usage does not increase as more simple filter rules are deployed. However, if the filter condition is too generic, it is possible that this rule can generate too many alerts, which will strain the system resources for the storage and retrieval of these alerts.
For example, you might write a rule to generate an alert when HTTP network activity arrives over a non-standard HTTP port.
Event Window Rule
This rule evaluates a set of events over a time period for specific conditions. At ingestion time, the rule is evaluated against a set of conditions. If those conditions are met, the event is retained in memory for a specific amount of time. After the specified time passes, the events are removed from the time window if the number of events collected does not meet the threshold to trigger an alert.
The memory consumption of such rules is highly dependent on the incoming event rate (traffic), the amount of data per event, and the time length specified in the event window. Each matching event is retained in memory until the time window has passed, so the longer the time window, the greater the potential volume. For example, you might write a rule that generates an alert if a user has five failed login attempts within a ten minute time frame.
Followed By Rule
This rule evaluates a chain of incoming events to determine if the sequence of events matches a particular condition. At ingestion time, the rule is evaluated against a set of conditions. If the conditions are met, one of two actions occurs:
In both cases, the event is retained in memory. The amount of resource usage is particularly sensitive to the customer environment for this type of rule. If the filter condition generates many event threads, resources are consumed for each new thread (in addition to the event). Additionally, if the end of the event thread is never met (that is, an alert is never generated), then the entire event is saved in memory indefinitely. For example, you might write a rule to generate an alert when a user fails to log in to a server, then performs a successful login, and then creates a new account.
When writing and deploying rules, you should be aware that rule memory usage and alert generation consume system resources. The sections below are designed to help you keep your usage at a healthy level and monitor for problems if systems are becoming overloaded.
Best Practices for Writing Rules
These are general guidelines for writing rules.
- Create alerts for actionable events. The purpose of an alert should be to notify you of an event that requires immediate and specific action. For events that do not require action, or only require you to have awareness of the event, you can create a report.
- Validate your ESA rules within the Rule Builder or Advanced EPL Rule Builder before you deploy them. To prevent errors in your rules and confirm that they generate the expected alerts, you can test the rule logic with JSON data within the rule builders. This capability is available in NetWitness Platform version 11.5 and later. For more information, see Validate an ESA Rule and Validate an Advanced EPL Rule .
- Configure new rules as trial rules so you can observe how they react in your environment. If you deploy new rules as trial rules, they will be disabled if the configured memory threshold is exceeded.
- Configure Alert notifications only after your rule testing and tuning is complete. This can help ensure you do not get flooded with notifications if a rule behaves differently than you expect.
- Rules need to be specific so that you limit resource usage. Use the following guidelines to limit usage:
- Make the filters on the rule exclude all but the necessary events for the rule to fire accurately.
- Make the size of your windows (window time for correlation) as small as possible.
- Limit the events that you include in the window: For example, if you only want to see IDS events, ensure that you only include those events in your time window.
- Add Memory Thresholds to ESA rules that use memory. For example, if a rule contains windows or pattern matching, configure a memory threshold for that rule. If the rule goes over the allotted memory threshold, it gets disabled individually and an error is displayed for that rule on the (Configure) > ESA Rules > Services tab. This capability is available in NetWitness Platform version 11.5 and later.
- Rules need to be tuned to an alert level that is manageable. If you are flooded with alerts, then the purpose and of an alert is lost. For example, maybe you want to know about encrypted traffic to other countries. But, you could limit the list to countries that are known risks. This limits the volume of alerts to a level you can manage.
For more best practice information for writing ESA rules, see ESA Rule Writing Best Practices.
Best Practices for Working with RSA Live Rules
These are guidelines for RSA Live Rules.
- Deploy RSA Live rules in small batches. Not every rule is suited to every environment. The best way to ensure your RSA Live rules are successful is to deploy them in small batches so you can test them in your environment. If you deploy small batches, it's much easier to tell if a particular rule has an issue.
- Read the rule descriptions provided with RSA Live rules. ESA rules are not “one size fits all.” Not all rules will work in your environment. The rule descriptions tell you which parameters you will need to modify to successfully deploy a rule in your environment.
- Set your parameters. RSA Live rules have parameters that need to be modified. If you do not modify your parameters, the rule may not work or it may exhaust your memory.
- Deploy new rules as trial rules so you can observe how they react in your environment. If you deploy new rules as trial rules, they will be disabled if the configured memory threshold is exceeded. For more details, see Working with Trial Rules.
Best Practices for Deploying Rules
These are general guidelines for deploying rules.
- Deploy rules in small batches so you can observe how they react in your environment. Not all environments are the same, and a rule will need to be tuned for memory usage, alert volume, and effective detection of events.
- Test rules before you configure alert notifications. Configure Alert notifications only after your rule testing and tuning is complete. This can help ensure you do not get flooded with alerts if a rule behaves differently than you expect.
- Monitor system health as a part of your deployment process. When you deploy rules, monitor your system’s health as a part of your deployment process. You can view total memory usage for your ESA in the Health and Wellness tab. For more information, see "View Detailed Statistics in Health and Wellness" in Troubleshoot ESA.
Best Practices for System Health
These are general guidelines for system health.
- Set up new rules as trial rules. A common issue is that new rules may cause memory issues. To prevent this, you can set up new rules as trial rules. If the configured memory threshold is met, all trial rules are disabled to prevent the system from running out of memory. For more information about trial rules, see Working with Trial Rules.
- Set up thresholds in Health & Wellness to alert you if memory usage is too high. There are metrics in NetWitness Platform Health & Wellness that track memory usage. You can set up alerts and notifications to send you an email if those thresholds are crossed. For more information about the memory statistics you can view, see View Memory Metrics for Rules.
- Monitor memory metrics for each rule in Health & Wellness. For each rule, you can view the estimated memory usage in Health & Wellness. You can use this information to ensure that rules do not use too much memory. For more information about the memory statistics you can view, see View Memory Metrics for Rules.