In the evolving landscape of cyber threats, password spraying has emerged as a persistent and stealthy tactic used by malicious actors to compromise user accounts. Unlike brute-force attacks that target a single account with multiple passwords, password spraying flips the script—using a few commonly used passwords across many accounts to avoid detection and account lockouts.

What Is Password Spraying?

Password spraying is a type of credential-based attack where adversaries attempt to gain unauthorised access by trying a small number of widely used passwords (like “Password123” or “Welcome1”) across a large number of usernames. This method is particularly effective against organisations with weak password policies or users who reuse passwords across platforms.

US Context and Real-World Impact

The US Cybersecurity Agency (ACSC) has reported a high volume of password spraying attacks targeting local organisations, particularly those using external-facing services such as Office 365, webmail, and remote desktop access. In one notable case, attackers exploited predictable username formats and weak passwords to gain access to corporate email systems, leading to data breaches and reputational damage.

These attacks often go unnoticed because they generate fewer failed login attempts per account, making them harder to detect using traditional security monitoring tools.

Common Mistakes and Pitfalls

Several factors contribute to the success of password spraying attacks:

• Weak or Default Passwords: Many users still rely on simple, guessable passwords.
• Lack of Multi-Factor Authentication (MFA): Without MFA, a compromised password is often all an attacker needs.
• Uniform Username Conventions: Predictable formats like firstname.lastname@company.com make it easier for attackers to guess valid usernames.
• Inadequate Monitoring: Many organisations lack the tools or configurations to detect low-and-slow attack patterns typical of password spraying.

Best Practices for Defence

To mitigate the risk of password spraying, the ACSC and cybersecurity experts recommend a multi-layered approach:

1. Implement MFA: Enforce multi-factor authentication across all external-facing services. This significantly reduces the risk of account compromise, even if a password is guessed.
2. Adopt Strong Password Policies: Encourage the use of passphrases and prohibit commonly used or breached passwords.
3. Monitor Authentication Logs: Use Security Information and Event Management (SIEM) tools to detect anomalies such as a high number of failed logins from a single IP or login attempts in alphabetical order.
4. Use Smart Lockout Features: For organisations using Active Directory Federated Services (ADFS), features like Microsoft’s Extranet Smart Lockout can help prevent account lockouts while still detecting malicious behaviour.
5. Educate Users: Regular training on password hygiene and phishing awareness can reduce the likelihood of credential compromise.

Final Thoughts

Password spraying is a low-cost, high-reward tactic for cybercriminals, and its prevalence in the US is a stark reminder of the importance of robust identity and access management. By understanding the threat and implementing layered defences, organisations can significantly reduce their exposure and build a more resilient cybersecurity posture.