Password spraying: Attack guide and prevention tips 

The phrase ‘spray and pray’ likely came from the military, used to describe inaccurately firing automatic weapons in the hope that one shot eventually found its mark. It’s now used to describe any scenario where a strategy relies on the sheer number of attempts overcoming any flaws in accuracy or skill. When it comes to cracking passwords, ‘spraying and praying’ can be a surprisingly effective method of attack. We’ll cover how password spraying works, some real-world examples, and strategies to keep your organization safe.

What is password spraying?

Password spraying is a technique where hackers try a set of commonly used passwords against many different user accounts, in an attempt to gain unauthorized access. Instead of targeting a single account with numerous password attempts (which can trigger security alerts) attackers spread their efforts across many accounts, using one or a few passwords at a time. This helps avoid triggering account lockouts and triggering security alerts.

Hackers favor password spraying because It’s a simple attack technique that exploits the human tendency to use simple, easily guessable passwords, rather than requiring technical skill to execute or reuse them across multiple accounts. It’s a low-risk, high-reward method. If once of the targeted accounts was using a common passwords and access is gained, they can often move laterally within the network to access valuable data.

Is password spraying a brute force attack?

Password spraying is related to brute force attacks but is distinct in its approach. Brute force attacks involve rapidly trying many different passwords on a single account until the correct one is found. Password spraying is the opposite – it’s about targeting many accounts with a small set of commonly used passwords. This idea is to avoid triggering the account lockout mechanisms that are often activated by repeated failed login attempts on a single account. It’s a more subtle attack, but would be less effective if trying to crack a password associated with a specific account.

How does a password spray attack play out?

Impacts of a password spraying attack

Hackers gaining unauthorized access to one of multiple user accounts is going to result in problems for an organization:

• Data breaches, theft of sensitive information, and potential financial losses
• Compromised accounts can be used to launch further attacks, spread malware, or conduct espionage
• Attack can disrupt services, causing downtime and operational disruption
• Reputational damage to an organization can erode trust among customers and partners

For IT and security teams, the knock-on impacts of a password spraying attack can be substantial:

• May need to invest significant time and resources in investigating the breach, identifying all compromised accounts, and resetting passwords
• Attention is diverted from other critical tasks and strains the team’s capacity
• Might need to enhance security measures, which can require additional training and support for users
• Could face increased scrutiny and pressure from management and regulatory bodies

Interested to know how many of your end users are using weak and easily-guessable passwords? Run a read-only scan of your Active Directory with our free tool: Download Specops Password Auditor.

Real-world example of a password spraying attack

A large botnet consisting of 130,000 devices recently targeted Microsoft 365 service accounts across the world with a password spraying attack. The attackers exploited Basic Authentication, which sends credentials in plaintext or base64 encoded form, to bypass multi-factor authentication (MFA). This method allows them to avoid triggering security alerts, making the attack difficult to detect. The attackers knew combining this exploit with password spraying would likely lead to success when tried against a large number of service accounts.

Signs your end users are being targeted

If your end users are being targeted with password spraying attacks, there are several signs to watch out for:

1. Failed login attempts: Password spraying is intended to avoid lockouts, but you might still see some suspicious failed login behavior. Perhaps a failed request every hour, even during unusual times such as late at night or early in the morning.
2. Other unusual activity: Users might observe unusual activity in their accounts, such as attempted logins from unfamiliar locations or devices, or unauthorized changes to account settings.
3. Security alerts: Your security systems might generate alerts for suspicious login patterns, such as multiple failed login attempts from the same IP address or a sudden spike in authentication requests.
4. Phishing attempts: Users might receive phishing emails or messages that attempt to trick them into revealing their credentials, which can be a precursor to a password spraying attack.
5. Anomalous network traffic: Network monitoring tools might detect unusual traffic patterns, such as a large number of login requests from a single IP address or a sudden increase in authentication traffic.

How to defend against password spraying attacks

Defending against password spraying attacks involves a multi-layered approach that combines technical measures, policy enforcement, and user education:

1. Add multi-factor authentication (MFA): MFA adds an extra layer of security by requiring users to provide a second form of verification, such as a code sent to their phone, in addition to their password. This makes it much harder for attackers to gain unauthorized access even if they have the correct password.
2. Enforce strong password policies: Avoiding common or easily guessable passwords is the key to defending against password spraying. Encourage users to create long passphrases of over 15 characters. Passphrases are made of three random words, making them easier to remember than strings of random characters.
3. Disable basic authentication: Basic Authentication sends credentials in plaintext or base64 encoded form, making it vulnerable to interception. Disabling this feature in your systems, especially in Microsoft 365, can significantly reduce the risk of password spraying attacks.
4. Monitor and analyze login attempts: Use security information and event management (SIEM) tools to monitor login attempts and detect unusual patterns, such as multiple failed login attempts from the same IP address or a sudden increase in authentication requests. Set up alerts to notify your security team of suspicious activity.

Looking for advice around securing ADFS? Detailed steps on securing Active Directory Federation Service against password spraying attacks can be found here.

Protect your passwords and logons

Specops Password Policy and Specops Secure Access are powerful tools that can help organizations significantly enhance their defenses against password spraying attacks:

• Specops Password Policy: Makes it simple to enforce strong, complex password requirements. You can set rules for minimum length, character types, and even ban common and easily guessable passwords. Your Active Directory will be continuously scanned against our growing database of over 4 billion compromised passwords.
• Specops Secure Access: Provides robust MFA options, which add an extra layer of security by requiring users to provide a second form of verification. This can include one-time codes sent to mobile devices, biometric authentication, or hardware tokens.

Integrating Specops Password Policy and Specops Secure Access into your security strategy builds a layered and robust defense against password spraying attacks. Want to know how they could fit with your organization’s needs? Let’s talk!

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