Password Attack Guide: What is Password Spraying, How It Works & How to Prevent It

Learn the inner workings of password spraying attacks and safeguard your online accounts

· Ethical Hacking
By Jan Brennenstuhl · 11min read

Password Attack Guide: What is Password Spraying, How It Works & How to Prevent It

Introduction to Password Attacks

Cybercriminals continuously seek new ways to gain account access and exploit security flaws as technology progresses. Password spraying is one such practice that, in recent years, has become popular among hackers looking to gain unauthorized access to accounts and sensitive information. But what exactly is password spraying, how does it work, and what can you do to prevent it? Let’s get started.

What is Password Spraying?

Password spraying is a well-defined (T1110.003) password attack in which hackers test several commonly utilized passwords to gain access to several user accounts. Malicious actors frequently prepare spraying attacks with reconnaissance and discovery techniques to learn more about the targeted account base. Often online services leak information in their sign-up or password reset processes. Password spraying then concentrates on trying common passwords across many known accounts.

The motivation behind password spraying attacks

As the cyber threat landscape evolves, threat actors’ focus shifts from assaulting computer networks to stealing user identities. Because of the increasing sophistication of software in detecting malware programs and vulnerabilities, attackers have been forced to adapt, resulting in a greater emphasis on identity-based attacks.

Many organizations invest considerably in securing user accounts by establishing complicated password policies and restricting access to resources from secure networks. While these precautions are vital best practices, they are frequently insufficient in the face of a compromised trusted user account.

How Password Spraying Works

Understanding a typical password spray attack is critical to protect against and investigate it. Password spray attacks are brute-force attacks that use an exhaustive list of usernames and link them with popular passwords to guess the proper combination for as many passwords and users as possible.

Advanced password spraying involves techniques that rely on people using variations of common passwords and often follow three key characteristics: multiple account targeting, common passwords and wordlists, and other dictionary attacks while flying low and slow under the radar.

Targeting Multiple Accounts

In a password-spraying attack, attackers target many accounts instead of focusing on one password or a single account. They avoid activating security measures such as account lockout policies or active blocking by spreading their efforts over numerous accounts.

Common Passwords & Dictionary Attack

Attackers employ lists of common passwords or customized dictionaries, pre-compiled lists of words, phrases, and character combinations likely to be used as passwords. These lists are frequently based on leaked password databases, increasing the likelihood that an attacker would find a match. The password top lists by OWASP are likely the most popular sources for common passwords.

The Use of Bots & Automation in Password Spraying

A determined malicious actor has to be patient. The most sophisticated password sprays will employ multiple IP addresses and not uncommonly involve botnets to simultaneously assault various accounts with a limited number of selected password guesses. Numerous password-spraying tools exist that help even less techy threat actors to automate brute-force attacks and password-spraying for multiple targets, protocols, and use cases. Due to their highly distributed and low frequent (“dripping”) characteristics, these credential-based attacks are hard to distinguish from natural authentication attempts and often remain undetected.

Password Spraying vs Brute-Force Attack

Password spraying is a type of brute-force attack. Both seek to guess passwords and identify matching user credentials; the primary distinction is how they do it. Traditional brute-force attacks target a single account and attempt all potential password combinations. This can take time and may result in account lockouts or security alerts. Password spraying, on the other hand, distributes the risk by targeting several accounts with fewer password attempts, making it harder to detect and more likely to succeed, especially given that many regular users reuse commonly used passwords across multiple sites. A password-spraying attack is a brute-force attack on steroids.

Password Spraying vs Credential Stuffing

Password spraying and credential stuffing are two different credential-based attacks used by attackers to exploit password vulnerabilities. Credential stuffing is a technique in which an attacker obtains a list of leaked credential pairs (username and password) from a prior data breach and attempts to use the same credentials against several accounts hoping to gain access to a valid account. Credential stuffing takes advantage of a list of known credential combinations, and many end-users reuse the same password across many accounts, which is more effective than password spraying. The dark web is full of more or less reliable stolen credentials.

Password Spraying vs Dictionary Attack

A dictionary attack is a brute force attack in which an attacker generates a password list by combining various words and phrases from a dictionary, hence the name “dictionary” brute force attack. While dictionary attacks and password spraying target passwords, their goals and methods differ. Dictionary attacks seek to exhaust all possible password combinations, whereas a password spraying attack aims to discover a common password used by numerous users. In both cases, attackers are hunting for easy-to-guess or regularly used passwords.

Real-World Examples of Password Spraying

Password spraying attacks never stop. The following three real-world examples of security incidents caused by password spraying attacks are just the tip of the iceberg:

  • Microsoft Office 365 Attack – In 2021, Microsoft observed a spike in password-spraying assaults against 250 Office 365 customers in the US and Israeli defense technology sectors. According to Microsoft, the credential-based attacks targeted critical infrastructure businesses in the Persian Gulf and were conducted by a group known as DEV-0343.
  • Parliament of the United Kingdom Attack – In June 2017, a password-spraying attack targeted the email accounts of members of the UK Parliament, resulting in remote access being blocked for MPs as a precaution.
  • Citrix Systems Attack – Between 2018 and 2019, hackers accessed Citrix systems and sensitive data over five months. The FBI alerted Citrix to the breach in March 2019 and stated that a password-spraying attack was the likely cause.
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How a Password Spraying Attack Affects Your Customers

Understanding password spraying risks and compromised security costs heavily depends on local threat scenarios, business contexts, and risk appetite. The most severe consequence of password spraying is often a loss of consumer trust. When a website or email account is compromised, there is no way to protect the customer’s personal information or sensitive data without extra passwordless security measures.

  1. Data Breaches & Identity Theft – Password spraying attacks allow fraudsters to gain unauthorized access to sensitive consumer data such as personal information, financial information, intellectual property, and login credentials. This information can be used to commit identity theft or resell on the dark web, placing your clients at risk of financial loss and long-term damage to e.g. their credit ratings.
  2. Loss of Trust – Customers provide businesses their personal information, expecting to be kept safe and secure. A compromised account caused by a password spraying attack can cause users to lose trust in your brand, resulting in decreased customer loyalty and potential loss of business.
  3. Disrupted Services – Credential-based attacks might cause your services to be unavailable, inconveniencing customers that rely on them. Downtime caused by an attack and active countermeasures might make it difficult for your consumers to access their accounts, make purchases, or use your services, leading to irritation and dissatisfaction.
  4. Financial Impact – If an attack is successful, customers may experience economic consequences due to unlawful transactions, fraudulent charges, or the cost of mitigating the effects of identity theft. These financial obligations can diminish the perceived value of your products or services, driving away customers.
  5. Privacy Concerns – When customers discover that their personal information has been exposed due to a password spraying attack, they may become more concerned about their overall privacy and be less willing to share information with a business in the future.

Detecting password spraying attacks 

The most critical exercise to enable effective password spray defense is to monitor and respond to suspicious activity by leveraging tools for detecting password spraying.

Sudden Spike in Failed Login Attempts

Examine account authentication attempts regularly and automatically to spot any failed logins or suspicious patterns. A high ratio of failed login attempts for different accounts in a short period could indicate an ongoing password-spraying attack.

Unusual Account Activity

Organizations vulnerable to spraying and other credential-based attacks should create user profiles for their accounts and overarching population profiles for their whole account base to discover login abnormalities. User profiles can assist in signaling suspected account activity coming from unexpected IP addresses, utilizing unique user agent identifiers, or other criteria by scoring the originality of an authentication attempt based on prior interaction data. If a user has previously successfully authenticated from a German IP using an iOS user agent, authentications for the same account from an Android smartphone in India should be noticed, considered malicious traffic, and (ideally) trigger additional authentication steps.

Population profiles are comparable but have a broader scope because they consider metadata such as location profiles, network profiles, and device information used throughout the customer base. If an organization’s business plan, for example, restricts service offers to specific users or regions, login attempts from other locations may result in a higher risk score. A company that only operates in Europe will most certainly flag sign-ins from China, resulting in additional actions or limited privileges.

Password spraying prevention

There are plenty of password spraying defense techniques and best practices available. The most effective threat mitigation is the abandonment of password-based authentication systems (knowledge factor) in favor of passwordless mechanisms. Because this is not currently practicable for many organizations, defense with multiple layers and reinforced authentication approaches is required.

IP-Blocking & Geo-Blocking

When preventing password spraying or distributed denial of service (DDoS), the ultimate last resort is to hard block individual IPs, entire CIDR ranges, ASNs, or regions. Of course, this will have a significant business impact and will only temporarily alleviate the pressure.

Bot Management

Because password spraying attacks frequently use automation tooling and large-scale botnets, automated bot recognition and management are critical for password spraying prevention. Because bot detection can not produce binary conclusions or sharp deny decisions, intermediary challenges, and further authentication steps are required.

Intermediary Challenges

There are at least two types of intermediary challenges: interactive challenges, such as CAPTCHAs, which require users to solve a puzzle to prove human interaction, and non-interactive challenges, such as proof-of-work-based mechanisms, which need a suspicious user agent to solve cryptographic exercises, significantly slowing automated efforts and raising operational costs for large-scale attacks.

Strong Password Policies and Best Practices

Implementing a firm password policy that encourages complex passwords and prohibits using regularly used passwords and compromised credentials does not necessarily prevent spray attacks. Bad actors will still attempt them, but it renders them virtually ineffective. I recently wrote about how to create a strong password policy that is user-friendly and effective, which you should read!

Passwordless Authentication

Passwordless authentication is a modern paradigm shift away from knowledge factors (passwords) and toward possession (like Passkeys) or inherence factors (biometrics). Passwordless login is the most effective password-spraying attack prevention because the primary target is removed. I recently described why passwordless sign-in is regarded as the future of cybersecurity; take a look!

Enable Multi-factor Authentication (MFA)

Two-factor authentication (2FA) and MFA incorporate at least two separate authentication concepts, with the passwordless access component always included. Regular password-based logins are frequently complemented by one-time passwords (OTP) produced in a separate authenticator app or device. Enable MFA to prevent password spraying attacks – many federated authentication providers support 2FA enforcement!

The Ongoing Battle Against Password Attacks

Password spraying attacks are only one example of how the cybersecurity landscape keeps evolving. As attackers create new strategies, companies and individuals must remain aware and proactive in their security procedures. Brute-force attacks, such as password spraying, can be considerably reduced by setting strong username and password guidelines, establishing multi-factor authentication, and cultivating a security-conscious culture.

Frequently Asked Questions (FAQs)

Can password spraying be easily detected?

Because of their low and slow nature, it might be challenging to detect password-spraying attacks. However, organizations can detect and prevent password-spraying attacks with the correct tools and monitoring.

How can I protect my personal accounts from password-spraying attacks?

To protect your personal accounts from password-spraying attacks, use unique passwords, avoid obvious passwords, enable 2FA, monitor attempts to gain access to your accounts regularly, use password managers, be aware of phishing emails, and keep your security measures up to date.

Are there any tools available to help detect and prevent password spraying?

Numerous technologies are available to detect and prevent password spraying attacks, like Security Information and Event Management (SIEM) systems, User and Entity Behavior Analytics (UEBA) tools, or dedicated edge protection services. Organizations should employ a combination of these tools and solutions to safeguard their networks and user accounts.

What should I do if I suspect password spraying compromised my account?

If you suspect your account has been hacked by a password-spraying attack, act quickly to protect your account and personal information. Change your password, apply two-factor authentication, notify the service provider, monitor your potentially compromised accounts, and update your security measures if you see any strange behavior.

Is it Possible to Prevent a Password Spraying Attack?

While 100% protection against brute-force attacks like credential stuffing or password spray attacks is difficult to ensure, implementing strong password policies, utilizing two-factor authentication, monitoring for suspicious activity, and training users and staff can considerably lower the likelihood of successful attacks.

Portrait of Jan Brennenstuhl
Written by Jan Brennenstuhl

Jan Brennenstuhl is a Principal Software Engineer at Zalando SE, balancing security with friction for their customers. He built an IAM team and brought single sign-on (SSO) to Europe's largest e-commerce fashion platform.