Password Spray Attacks: How They Work and How to Stop Them

About 8 min read

Password spray attacks are among the hardest cyberattacks to detect in recent years, and many organizations and individuals have fallen victim. According to Microsoft's 2024 Digital Defense Report, password spray attacks account for approximately 40% of all identity-based attacks, an increasing trend year over year. CISA (the U.S. Cybersecurity and Infrastructure Security Agency) also issued an advisory on password spray attacks in 2024, noting a sharp rise in cases targeting cloud service accounts. As of 2025, attackers have been observed using AI to automatically collect employee information from target organizations and generate more accurate password lists. Unlike traditional brute force attacks, this approach bypasses authentication in a different way, making it difficult to defend against with conventional security measures. This article explains how password spray attacks work in detail and introduces effective defenses using passtsuku.com.

What Is a Password Spray Attack?

A password spray attack is a technique in which a small number of commonly used passwords are tried in sequence against a large number of accounts. For example, the password "password123" is tried once against 10,000 accounts, then "123456" is tried against the same 10,000 accounts, and so on.

The ingenuity of this technique lies in the extremely low number of attempts per account. Many services trigger account lockout after consecutive failed logins to the same account, but in a password spray attack, attempts per account are limited to 1-2, staying below the lockout threshold.

Differences from Brute Force Attacks

A brute force attack is a technique that tries every possible password combination against a single account. The attack focuses on a small number of accounts, generating a large volume of login attempts in a short time. As a result, it can be relatively easily detected and defended against through account lockout and rate limiting.

In contrast, password spray attacks are fundamentally different in that they attack "broadly and shallowly." Attackers obtain lists of thousands to millions of accounts and try only a very small number of passwords against each. From the perspective of any individual account, it is indistinguishable from a normal login failure, slipping past security system monitoring. This "low-frequency, wide-range" characteristic is the fundamental reason why detection by SIEM (Security Information and Event Management) and IDS (Intrusion Detection Systems) is so difficult. Rule-based monitoring that detects anomalies in a single account cannot capture the overall attack pattern.

For more on detecting password spray attacks, see SIEM log analysis and attack detection books (Amazon).

Password Lists Used by Attackers

Passwords used in password spray attacks are based on lists of "commonly used passwords" collected from past data breach incidents. According to security researchers, the following types of passwords consistently rank at the top each year.

• Classic passwords such as "123456," "password," and "qwerty"
• "Welcome1," "Password1," and similar passwords that minimally include an uppercase letter and a number
• "Summer2024," "Spring2025," and other combinations of seasons and years
• "Company123" and similar combinations of organization names and numbers
• Frequently used phrases such as "abc123," "letmein," and "iloveyou"

Attackers constantly update these lists, analyzing trends from newly leaked databases. You should assume that any password a human finds "easy to remember" is almost certainly on these lists. A common misconception is thinking "adding my own twist makes it safe," but substitution patterns like replacing "a" with "@" or adding "!" at the end are already covered in attacker lists.

Techniques for Evading Account Lockout

One reason password spray attacks are effective is that they cleverly evade account lockout mechanisms. Attackers combine the following techniques.

• Limiting attempts to each account to once, staying below the lockout threshold (typically 3-5 attempts)
• Spacing attempts hours to days apart to evade rate limiting
• Distributing attacks from multiple IP addresses to avoid IP-based blocking
• Mimicking legitimate login flows to evade bot detection

Through these techniques, attacks proceed quietly over weeks to months. It is not uncommon for victims to discover that multiple accounts have already been compromised by the time they notice.

An important edge case to note is that attackers may target legacy authentication protocols of cloud services (IMAP, POP3, SMTP Basic Auth, etc.). Since these protocols can bypass multi-factor authentication (MFA), it is crucial to also configure policies that only allow modern authentication. For organization-wide password practices, see our corporate password policy guide. Additionally, implementing two-factor authentication is one of the most effective defenses against password spray attacks.

For more on legacy authentication vulnerabilities and zero trust authentication design, see zero trust authentication and legacy protocol security books (Amazon).

Defenses Using passtsuku.com

The most effective defense against password spray attacks is to use random passwords that are not on attacker password lists. Passwords generated by passtsuku.com are based on cryptographically secure random numbers, making the probability of matching a commonly used password list virtually zero.

Recommended Settings

To generate passwords resistant to password spray attacks with passtsuku.com, the following settings are recommended.

• Length: Set to 16 characters or more
• Enable all 4 character types: uppercase, lowercase, digits, and symbols
• Verify that the generated password strength meter shows 80 bits or more

Since passwords generated by passtsuku.com are completely random strings, they have an entirely different composition from attacker lists containing "password," "123456," or "Welcome1." By generating a different password for each service and managing them with a password manager, you can significantly reduce the risk of password spray attacks.

Reviewing Existing Passwords

We also recommend reviewing passwords for services you are already using. In particular, passwords set with memorability as a priority or passwords reused across multiple services are easy targets for password spray attacks. Replace them with new random passwords generated by passtsuku.com. The highest priority for change should be email accounts, financial services, and work-related service passwords. Email accounts should be the top priority because email is used for password resets on other services - if your email is compromised, other accounts are put at risk in a chain reaction. See also our article on the importance of protecting your email account.

Comparing Password Spray Attacks with Other Attack Methods

To properly understand password spray attacks, let us organize the differences from similar attack methods.

• Brute force attack: Tries all patterns against 1 account. Easy to detect, but still a threat in offline attacks
• Password spray attack: Tries a small number of passwords against many accounts. Difficult to detect
• Credential stuffing: Tries leaked credentials directly on other services. Relies on password reuse
• Dictionary attack: Attacks 1 account using a word list. An optimized version of brute force

The common defense against all these attacks is to generate random passwords with a tool like passtsuku.com and use a different password for each service.

What You Can Do Right Now

1. Generate a random password of 16 characters or more with passtsuku.com and replace the passwords for your email account and work services
2. Check all your accounts for commonly used passwords such as "123456," "Password1," and "Welcome1"
3. Enable multi-factor authentication on your cloud services and disable legacy authentication protocols
4. Check your email address for leaks on Have I Been Pwned and immediately change the password for any service where a leak is found

Frequently Asked Questions

What is the difference between password spraying and brute force attacks?

Brute force tries many passwords against one account, while password spraying tries one common password against many accounts. It evades account lockout thresholds, making it harder to detect.

Which services are most targeted by password spray attacks?

Cloud services widely used by enterprises, such as Microsoft 365, VPN gateways, and remote desktop, are primary targets. They have internet-facing login pages and predictable usernames (email format), making them easy to attack.

How can individual users protect themselves from password spray attacks?

The best defense is to never use common passwords like "123456", "password", or "qwerty". Generate random strings with a password generator and enable two-factor authentication to virtually neutralize password spray attacks.