Using AWS CloudWatch to monitor Centrify Audit Trail events in EC2 Windows instances

Background

As more and more organizations run infrastructure in IaaS platforms like Amazon AWS, there's an increased need to enhance security operations and prove effective implementation of security controls.  AWS provides a solution set that includes CloudWatch.  

About CloudWatch

As defined by Amazon "CloudWatch monitors your Amazon Web Services (AWS) resources and the applications you run on AWS in real time. You can use CloudWatch to collect and track metrics, which are variables you can measure for your resources and applications." 

For more information, check out the Getting Started guide for CloudWatch:
https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/WhatIsCloudWatch.html

The goal of this article, is to provide some initial guidance to leverage AWS CloudWatch to collect, track and measure Centrify Audit Trail events in Windows systems running in AWS.

For a companion article that covers UNIX/Linux instances, click here: http://centrifying.blogspot.com/2017/04/using-aws-cloudwatch-to-monitor.html 

About Centrify Audit Events

Centrify Audit Events (CentrifyAuditTrail) is the cross-platform framework used by Centrify Server Suite to document and provide access, privilege and audit trail event data. When a Centrify-enabled service is invoked, an audit trail event is written to UNIX syslog or Windows event log.  These events are documented in the  Audit Events Administrator's Guide for the current version of Server Suite.  The types or content of the events vary depending on the edition (Standard or Enterprise)

For more information, check out the current guide for Server Suite 2017: https://docs.centrify.com/en/css/suite2017/centrify-audit-events-guide.pdf

Pre-Requisites

For this lab, you'll need:

• An AWS Account with the proper VPC setup, privileges in CloudWatch and IAM
• Active Directory (run by you or managed by Amazon) and the proper VPC name resolution and communications
• A Centrify zone, sample users and access/privilege setup
• At least one Windows system joined to Active Directory and the Centrify zone
• The Windows system should have some Centrify data (e.g. access, privilege elevations) present in the application event log.

Centrify AWS Lab:  You'll need to be at Standard Edition level to follow this lab, more info here:

http://community.centrify.com/t5/TechBlog/Labs-Setting-up-an-AWS-Test-Lab-for-Centrify/ba-p/27771

Implementation Overview

1. Set-up your AWS Windows Instances for CloudWatch Logs (use AWS's docs)
2. Verify Centrify Audit Trail events in the CloudWatch log group
3. Identify Access and Privilege-related Metrics provided by Centrify
4. Create the Filters and Assign a Metric
5. Create a Dashboard
6. Create an Alarm

Set-up your AWS Linux Instances for CloudWatch Logs

For information on this topic, please review AWS's documentation:
http://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/UsingConfig_WinAMI.html#send_logs_to_cwl

Note that Centrify Audit Trail resides in the Windows Application log.  To gather the proper event data, make sure you are capturing information and warning messages, this is configured by modifying the AWS.EC2.Windows.CloudWatch.json file in the proper location based on your deployment (stand alone or using SSN service) and under teh ApplicationEventLog stanza, setting the Levels to 7 as illustrated below:

{
    "Id": "ApplicationEventLog",
    "FullName": "AWS.EC2.Windows.CloudWatch.EventLog.EventLogInputComponent,AWS.EC2.Windows.CloudWatch",
    "Parameters": {
        "LogName": "Application",
        "Levels": "7"
    }
},

Once you have the Windows logs logs for your instances in the corresponding Log Group, please proceed to the next section.

Verify Centrify Audit Trail events in the CloudWatch log group

1. Go to your CloudWatch console: https://console.aws.amazon.com/cloudwatch/home
2. Click on Logs > Click on the log group for your Windows instances (e.g. "Default-Log-Group"  or the group you are using for your Windows event logs)
3. Click on Search log group and in filter events, type "AUDIT_TRAIL"
4. Verify the results.
    
   If you have a Windows system that was joined to the Centrify zone, there will be event data about access, privileges and other activities.

Now you have verified that your systems are streaming syslog data with Centrify Audit Trail information.

Identify Access and Privilege-related Metrics provided by Centrify

The Centrify Agent for Windows™ provides access control,multi-factor authentication and role-based privileged elevation; this component is called DirectAuthorize.  DirectAuthorize controls how users access the system and what commands they can run. The implementation of privilege elevation leverages roles defined in Active Directory and the DirectAuthorize client for Windows.

Example 

The metrics that you'll track will depend in your objectives and in your maturity level.  For illustration purposes, let's track successful and unsuccessful access and privilege elevation in my Windows EC2 instances. After reviewing the Centrify Audit events guide, I identify the following events:

Access Control

Windows Remote Login Success:  These events are recorded when an authorized user from the Centrify zone is succesfully granted access to the Windows system;  the Centrify Event Id is 6003.

You can leverage the Audit Trail admin guide for a full catalog.

Windows Remote Login Failure:  The opposite of the event above, it's a warning stating that the user was not authorized to log in from the current station.  This may denote an attempt at lateral movement. The Event Id is 6011.
 

Privilege Elevation

Run with Privilege Success:  Indicates successful privilege elevation the Centrify Agent for Windows; this may be a privileged desktop or an application; the event ID is 6012.
  

Run with Privilege Success:  Indicates an unsuccessful attempt at privilege elevation the Centrify Agent for Windows; this may be a privileged desktop or an application and could be user error or an abuse attempt; the event ID is 6018.

Create the Filters and Assign a Metric

1. Go to your CloudWatch console: https://console.aws.amazon.com/cloudwatch/home
2. Click on Logs and select the radio buttion next to your log group (e.g. Default-Log-Group)
3. Click Create Metric Filter
   • In filter pattern, type: centrifyEventID=6003
   • Press "Assign Metric" 
4. In Filter Name, type a unique name for the filter
5. In Metric details, create a new namespace (e.g. CentrifyAuditTrail) or browse for it if you already have it.
6. In Metric name, give it a descriptive metric.
   
7. Press Assign Metric.
8. Repeat the process for all the metrics you've identified.

Create a Dashboard

Before creating a dashboard, you may want to plan how to visualize the data.  In some instances it's useful to see the aggregate data (# of events), in others it's useful to see a trend (graphs overlapped with time).

Once you have thought of how to visualize the data, it's time to get started with your Dashboard. 

1. Go to your CloudWatch console: https://console.aws.amazon.com/cloudwatch/home
2. Click on Dashboards > Create Dashboard and give it a name, then press Create Dashboard
3. To add aggregated information, select the Number widget
4. Select your Namespace, Dimension and check the metric(s) to be measured
5. Go to the graphed metrics tab, and select the proper statistic and period  (e.g. sum and 1 day) and press Update Widget.
6. Once you have the Widget in the dashboard, adjust the size and label.

Repeat the process with the trend using with a line or stacked area.

Below is a simple dashboard that includes the metrics above.

 

Create an Alarm

A meaningful alarm could be based on a pattern outside expected behavior, an availability issue or another event (or aggregation of events) based on the risk that wants to be corrected.  This example is for illustration purposes only.

Example:  The threshold for attempted abouse of privilege elevation feature of the Centrify Agent for Windows for  3 or more attempts within a 5 minute period, when this happens, an email should be triggered to the members of the Security Operations distribution list.

1. Go to your CloudWatch console: https://console.aws.amazon.com/cloudwatch/home
2. Click Browse Metrics and next to Centrify-dzdo-Denied, click the alarm icon.
3. In create alarm:
   Name: Alarm-DZWin-Privilege-Abuse
   Whenever: is equal or greater than 3 for 1 consecutive period
   Period: 5 minutes
   Statistic: Sum
4. Actions
   Whenever this alarm state is Alarm
   Create a new list (secops@your-domain.com)

Trigger the alarm

1. Sign-in to your Windows instance with your administrator
2. For any application in your desktop, right click and select "Run with Privilege" 
3. You should get this message:
   
4. Repeat 3 more times.  This should trigger the alarm.
   
5. Review the Dashboard.  After a few minutes, the alarm will return to normal and you'll be notified
   

Conclusion

We have only scratched the surface of the capabilities provided by AWS CloudWatch, however in the context of Identity and Access Management, the enrichment of security operations via logs, alerts and dashboards should be done via standard tools; otherwise if each tool duplicates these capabilities, then security operations won't know where to go first.  Centrify provides native plugins for Splunk, IBM QRadar and HP ArcSight.  These tools provide both operational data as well as like the following privilege command pie chart.

Related Articles

CloudWatch and Centrify EC2 Linux:  http://centrifying.blogspot.com/2017/04/using-aws-cloudwatch-to-monitor.html