Microsoft Sentinel SOC 101: How to Detect and Mitigate Brute Force Attacks with Microsoft Sentinel

Brutish

Get this entire series in a free, downloadable eBook https://aka.ms/SentinelSOC101

Brute force attacks are one of the most common and concerning security threats that organizations face today. These attacks involve an attacker attempting to gain unauthorized access to a system or account by systematically trying different passwords or passphrases until they find the correct one. Detecting and mitigating these attacks is crucial to maintaining the security and integrity of your systems.

The goal of a brute force attack is to exploit weak or easily guessable passwords and gain unauthorized access to a system. Attackers often use automated tools that can generate and test thousands of password combinations within a short period. These attacks can target various entry points, such as user accounts, remote desktop protocols (RDP), or SSH management ports. As a result, organizations need robust security measures in place to detect and prevent these attacks effectively.

Let’s explore how you can leverage Microsoft Sentinel, a cloud-native Security Information Event Management (SIEM) and Security Orchestration Automated Response (SOAR) solution, to effectively detect and respond to brute force attacks. Let’s talk about the necessary prerequisites, the collection of security events, the configuration of Azure Sentinel, and the creation of analytic rules to identify and mitigate these attacks. And then, let’s talk about how to simulate a brute force attack to test your detection capabilities.

Collecting Security Events

To detect brute force attacks, organizations must collect and analyze security events. Microsoft Sentinel provides a comprehensive set of tools and data connectors to gather relevant security logs and events from various sources. By centralizing these logs in a log analytics workspace, organizations can perform in-depth analysis and create custom detection rules.

One crucial security event to monitor is the Windows Event ID 4625, which indicates failed login attempts. By focusing on successive failed logins, organizations can identify potential brute force attacks. The log analytics workspace in Microsoft Sentinel enables organizations to query and analyze these security events effectively.

Creating Analytic Rules for Brute Force Attacks

Once the security events are collected and stored in the log analytics workspace, organizations can create analytic rules to detect brute force attacks. Analytic rules in Microsoft Sentinel allow organizations to define specific conditions and patterns that indicate a potential attack.

To create an analytic rule for brute force attacks, organizations can leverage the power of the Kusto Query Language (KQL) in Microsoft Sentinel. KQL enables organizations to query the collected security events and filter them based on specific criteria. By using KQL, organizations can create rules that detect specific Event IDs, like Event ID 4625, and filter for failed login attempts with certain substatuses.

For example, a KQL query to detect brute force attacks targeting RDP or SSH management ports could be:

SecurityEvent
| where EventID == 4625
| where (SubStatus == "0xc000006A" or SubStatus == "0xc0000064")
| project TimeGenerated, EventID, WorkstationName, Computer, Account, LogonTypeName, LogonType, LogonProcessName, SubStatus, Activity

This query filters for Event ID 4625 (failed logins) and specific substatuses indicating a brute force attack on RDP or SSH management ports. By creating an analytic rule based on this query, organizations can automatically detect and respond to brute force attacks.

Simulating Brute Force Attacks

To test the effectiveness of the analytic rules and detection mechanisms, organizations can simulate brute force attacks. Simulating attacks allows organizations to evaluate the responsiveness and accuracy of their detection rules and identify any potential gaps in their security measures.

Other than writing a tool (PowerShell or otherwise) to simulate a Brute Force attack, tools like Kali Linux and Hydra can be used to simulate brute force attacks. These tools enable organizations to automate the process of trying different passwords and passphrases against targeted user accounts or entry points. By running these simulated attacks and monitoring the alerts generated by Microsoft Sentinel, organizations can fine-tune their detection rules and improve their overall security posture.

See:

Preventing Brute Force Attacks

While detecting and responding to brute force attacks is essential, organizations should also implement preventive measures to mitigate the risk of such attacks. Here are some best practices to prevent brute force attacks:

Enforce Strong Password Policies

Implementing strong password policies is crucial to prevent brute force attacks. Organizations should enforce password complexity requirements, such as a minimum length, a combination of uppercase and lowercase letters, numbers, and special characters. Additionally, regularly educating users about the importance of strong passwords and password hygiene can further enhance security.

Implement Account Lockout Policies

Account lockout policies can help mitigate the impact of brute force attacks. By setting thresholds for failed login attempts, organizations can automatically lock user accounts temporarily or permanently. This prevents attackers from making unlimited login attempts and significantly reduces the success rate of brute force attacks.

Implement Multi-Factor Authentication (MFA)

Multi-factor authentication adds an extra layer of security and makes it significantly harder for attackers to gain unauthorized access. By requiring users to provide additional verification, such as a code sent to their mobile device or a fingerprint scan, even if an attacker manages to guess the password, they would still need the additional factor to gain access.

Implement Rate Limiting

Rate limiting can be an effective strategy to prevent brute force attacks. By limiting the number of login attempts per second or per minute, organizations can significantly slow down the attackers' progress. This makes it impractical for attackers to guess passwords within a reasonable timeframe, discouraging brute force attacks.

Monitor and Analyze Logs

Continuous monitoring and analysis of security logs are crucial to detecting and mitigating brute force attacks. By regularly reviewing the logs and looking for patterns of failed login attempts, organizations can proactively identify potential brute force attacks and take appropriate action such as those outlined as mitigations, including:

1. Implement a lockout policy: Implement a lockout policy that will lock out the account after a certain number of failed login attempts. This will prevent attackers from trying multiple passwords on the same account.

2. Use strong passwords: Strong passwords with a combination of letters, numbers, and symbols will make it harder for attackers to guess the password.

3. Implement two-factor authentication: Two-factor authentication adds an extra layer of security by requiring a second form of authentication, such as a fingerprint or a code sent to a mobile device.

4. Monitor network traffic: Monitoring network traffic can help detect brute force attacks and other suspicious activity.

5. Implement intrusion detection and prevention systems: Intrusion detection and prevention systems can help detect and prevent brute force attacks by monitoring network traffic and blocking suspicious activity.

6. Conduct regular security audits: Regular security audits can help identify vulnerabilities and weaknesses in the system and allow for timely remediation.

7. Report the attack: If an attack is detected, it should be reported to the relevant authorities, such as law enforcement or the organization's security team.

Summary

Brute force attacks pose a significant threat to organizations' security and can lead to data breaches and unauthorized access. However, with the robust capabilities of Microsoft Sentinel, organizations can detect and prevent these attacks effectively.

By collecting and analyzing security events, creating analytic rules, and simulating attacks, organizations can proactively detect brute force attacks and respond promptly. Additionally, implementing preventive measures such as strong password policies, account lockout policies, multi-factor authentication, rate limiting, and continuous log monitoring can significantly enhance the security posture of organizations.

With Microsoft Sentinel as a powerful security analytics and threat intelligence platform, organizations can stay one step ahead of attackers and protect their valuable data and resources from brute force attacks. By leveraging the capabilities of Microsoft Sentinel, organizations can detect, prevent, and remediate brute force attacks, ensuring the security of their digital assets.

---

[Want to discuss this further? Hit me up on Twitter or LinkedIn]

[Subscribe to the RSS feed for this blog]

[Subscribe to the Weekly Microsoft Sentinel Newsletter]

[Subscribe to the Weekly Microsoft Defender Newsletter]

[Subscribe to the Weekly Azure OpenAI Newsletter]

[Learn KQL with the Must Learn KQL series and book]

[Learn AI Security with the Must Learn AI Security series and book]