Author Archives: igorandri

Responding a security event is the core practice in the modern security frameworks. After a potential threat was detected, it is time to act. The shorter the response time is the less damage an attacker can deal to your cloud.

Detection in Azure

Azure Security Center in the Standard pricing tier ($15/VM node per month) comes with automated detection mechanisms. The core detection capability is built around real-time traffic and system logs parsing and applying machine learning algorithms to it:

A single dashboard can be found under Security Center -> Security Alerts blade and also on the main page of the Security Center:

Alerts represent single or multiple security events of the same nature and time span. Incidents are created from multiple alerts which are classified as related to each other – for example, an attacker runs a malicious script, extracts local password hashes and cleans the event log. This sequence of action will generate one incident.

Incident forensics

Incidents can be investigated in a forensics tool Investigation Dashboard (in the preview, as of May 2018). This tool draws the relationships between alerts, events that caused the alert, affected resources, users. It also can help when reconstructing lateral movements of attackers within the network.

Automated response

Incident forensics represents a post-mortem investigation. An adversary event did happen, and the attackers have already done some damage to the enterprise. We don’t have to wait until malicious actors finish their job – we can start acting right after getting the first signals about the intrusion. Alerts are generated by Azure in real-time, and recently Security Center got a powerful integration with Azure Logic Apps.

Logic Apps in Azure represent workflows of actions with pre-built triggers, conditions, and actions which include a wide range of both native and 3-rd components. For example, your logic app can listen to RSS feed and automatically tweet once new pages are published to the feed. Or, run a custom powershell through Azure Automation.

One of the recent additions to Logic Apps – Security Center triggers. This feature turns Azure security alerts into the powerful tool for fighting attackers once they trip a wire.

You can Security-related Azure Logic Apps under Security Center -> Playbooks (Preview).

Building the logic

After adding a new playbook, a user gets presented with Loic App Designer. The trigger is pre-populated – When a response to Azure Security Center alert is triggered. Once we get an alert, the playbook is executed. Then, we add a condition – there are multiple parameters that the alert arrives with. Let’s take “Alert Severity” and set the condition to High:

Other alert parameters include Confidence Level, Alert Body, Name, Start or End Time and many more. The range is quite broad which makes it possible to generate very specific responses to almost any imaginable event.

Now, if the condition is TRUE – Alert Severity is High, we want to contain the threat. One of the ways to do so is to isolate a VM under attack. Let’s say, assign it to a different Network Security Group which has no connection to the internal company network or some of its segments. To do it, we would need to get a VM name from the alert and run some Azure Powershell performing the NSG re-assignment.

Creating the Automation Job

Now, we can go to Azure Automation and create an Automation Job for our needs. This can be done through the blades Automation Accounts -> Runbooks -> Add a runbook. As Runbook type, choose “Powershell”.

Then, we insert the following code:

Param(
[string]$VMName
)

$connectionName = "AzureRunAsConnection"

try
{
# Get the connection "AzureRunAsConnection "
  $servicePrincipalConnection=Get-AutomationConnection -Name $connectionName

  Add-AzureRmAccount `
    -ServicePrincipal `
    -TenantId $servicePrincipalConnection.TenantId `
    -ApplicationId $servicePrincipalConnection.ApplicationId `
    -CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint
}

catch {
  if (!$servicePrincipalConnection)
  {
     $ErrorMessage = "Connection $connectionName not found."
     throw $ErrorMessage
} else {
  Write-Error -Message $_.Exception
  throw $_.Exception
  }
}

# Get VM object
$vm = Get-AzureRmVM -Name $VMName -ResourceGroupName AzureBootcamp
# Get NIC
$Nic = Get-AzureRmNetworkInterface -ResourceGroupName AzureBootcamp | Where-Object {$_.VirtualMachine.Id -eq $vm.Id}
# Change Network Security group to IsolatedNetworkNSG
$Nic.NetworkSecurityGroup = Get-AzureRmNetworkSecurityGroup -ResourceGroupName AzureBootcamp -Name "IsolatedNetwork-NSG"
# Apply changes
Set-AzureRmNetworkInterface -NetworkInterface $Nic