What is Password Spraying?

Password spraying is a type of brute-force attack where a threat actor attempts to use a single, commonly used password against many different accounts. This ‘low-and-slow’ method avoids triggering account lockouts that typically occur after multiple failed login attempts on a single account, making it difficult to detect.

Unlike a traditional brute-force attack that hammers a single account with thousands of password combinations, spraying works horizontally. The attacker takes one weak password, like ‘Winter2024!’, and tries it against a long list of usernames. If it fails, they simply move to the next username on the list.

This technique is deceptively simple but highly effective. It exploits the human tendency to use weak, predictable, or seasonal passwords. By only trying one or two passwords per account over an extended period, the attacker stays below the radar of most basic security monitoring tools.

The rise of cloud services and federated identity systems like Microsoft 365 and Google Workspace has made this attack vector even more popular. A single compromised account can provide a gateway to an entire ecosystem of sensitive data and applications, making the potential reward for the attacker very high.

The Technical Mechanics of a Password Spraying Attack

Understanding how a password spraying attack works is crucial for building an effective defense. The process is systematic and often automated, allowing attackers to target organizations of any size with minimal effort. It typically unfolds in a few distinct phases.

First, the attacker performs reconnaissance to build a target list of valid usernames. This is often the easiest part of the attack. They can harvest email addresses from a company’s website, scrape professional networking sites like LinkedIn, or purchase lists from previous data breaches on the dark web.

The goal is to gather as many legitimate usernames as possible that belong to a single organization. For an attack against a company’s VPN or email server, this means finding employee email formats, such as ‘firstname.lastname@company.com’.

Next, the attacker selects a small list of potential passwords. These are not random. They are carefully chosen based on common password patterns. Attackers often use seasonal passwords like ‘Spring2024’ or ‘Q22024’ because they know employees are often forced to change passwords periodically and use predictable patterns.

Other popular choices include the company’s name followed by a number (‘CompanyName123’), local sports teams, or default application passwords. The list is kept very short, often containing just one to five passwords for the initial spray.

The execution phase is where the ‘spraying’ happens. Using automated tools and scripts, the attacker attempts to log in to every account on their list using the first password. The script sends a single login request for ‘user1@company.com’ with the password ‘Winter2024’. If it fails, it moves to ‘user2@company.com’ with the same password.

This process continues through the entire list of usernames. By attempting only one login per user, the attack does not trigger the typical ‘three-strikes-and-you’re-out’ account lockout policy that protects individual accounts. To security systems, it looks like many different users just happened to forget their password once.

To further evade detection, attackers use sophisticated methods. They often distribute the attack across a botnet, a network of compromised computers. This means login attempts come from hundreds or thousands of different IP addresses, making it difficult to block the attacker based on a single source IP.

They also introduce timing delays between login attempts. Instead of trying hundreds of accounts per minute, they might slow the pace to a few per hour. This ‘low-and-slow’ approach is designed to blend in with normal network traffic and defeat security systems that look for high-volume attacks.

The attack cycle may be repeated. If the first password, ‘Winter2024’, yields no results, the attacker will wait a period of time, perhaps an hour or a day, before starting again with a new password like ‘Password123!’. This resets any short-term lockout counters and continues the hunt for a weak credential.

Once a valid username and password combination is found, the attack succeeds. The attacker now has an initial foothold inside the organization’s network. This single compromised account becomes a launchpad for further malicious activity, such as data exfiltration, ransomware deployment, or financial fraud.

Tools Used in Password Spraying

Attackers do not perform these attacks manually. They rely on a variety of specialized tools to automate the process. These tools are often publicly available and used by both malicious actors and security professionals for penetration testing.

• Hydra: A popular and fast network logon cracker which supports numerous protocols. It can be configured to cycle through a list of usernames with a single password.
• Metasploit Framework: This comprehensive penetration testing tool includes auxiliary modules specifically for password spraying against services like SSH, VNC, and Microsoft SQL Server.
• Kerbrute: A tool used specifically for password spraying against Microsoft Active Directory accounts without triggering account lockouts. It validates credentials against the Kerberos authentication protocol.
• Custom Scripts: Many attackers use custom scripts written in languages like Python or PowerShell. These scripts can be tailored to target specific login portals, handle session cookies, and incorporate advanced evasion techniques like IP rotation and randomized timing.

Case Studies: The Real-World Impact of Password Spraying

Theoretical explanations are useful, but seeing how these attacks unfold in real scenarios highlights the true danger. The following case studies illustrate how password spraying impacts different types of organizations and the steps taken to remediate the damage.

Case Study A: E-commerce Retailer Suffers Account Takeovers

A mid-sized online retailer, ‘Urban Threads’, noticed an increase in customer complaints about fraudulent orders. Customers reported receiving shipping notifications for items they never purchased. The support team was overwhelmed with requests for refunds.

An investigation revealed that dozens of customer accounts had been compromised. The attacker had gained access, added new shipping addresses, and used the customers’ saved payment information to order high-value electronics. The attack pattern was unusual; there was no sign of a database breach.

Further analysis of login logs showed the tell-tale sign of a password spray. Over 48 hours, login attempts from a wide range of IP addresses targeted thousands of customer accounts. The attacker used a single password, ‘Welcome2023!’, which was a default password the retailer had once suggested to new users. A small percentage of customers had never changed it.

The financial impact was immediate. Urban Threads had to cover the cost of the fraudulent orders, issue refunds, and pay for credit monitoring services for affected customers. The reputational damage was worse, with negative reviews and social media posts eroding customer trust.

To fix the issue, the company immediately forced a password reset for all users. They implemented a stronger password policy and deployed Multi-Factor Authentication (MFA) as a mandatory step for all logins. They also configured their systems to detect and flag impossible travel scenarios, such as an account logging in from New York and then from Moscow ten minutes later.

Case Study B: B2B SaaS Company’s Internal Network Breached

A B2B software company, ‘InnovateSoft’, prided itself on its security. They had firewalls, intrusion detection systems, and strict account lockout policies. However, their security was focused on protecting individual accounts from repeated failed logins.

An attacker compiled a list of employee email addresses from LinkedIn. They then initiated a very slow password spraying attack against the company’s Office 365 tenant, trying just one password, ‘Q42023!’, over several days. This slow pace did not trigger any alerts.

The attack successfully compromised the account of a marketing intern. While this account had limited privileges, it provided the attacker with a crucial foothold. They used the intern’s access to browse internal SharePoint sites, identify key personnel from organizational charts, and craft highly convincing phishing emails.

The attacker then launched a targeted phishing campaign from the compromised internal account, tricking a system administrator into revealing their credentials. With administrative access, the attacker was able to deploy ransomware, crippling the company’s operations and demanding a seven-figure ransom.

The remediation was costly and complex. InnovateSoft had to hire a cybersecurity incident response firm to contain the breach and restore systems from backups. They learned a hard lesson: a single compromised low-privilege account can be enough to bypass a strong perimeter. The fix involved deploying MFA across all accounts, implementing a security information and event management (SIEM) system to correlate login events across the entire organization, and providing extensive employee security training.

Case Study C: Healthcare Provider’s Patient Data Exposed

A regional healthcare provider, ‘HealthFirst Clinic’, operated a patient portal where individuals could access their medical records and communicate with doctors. An attacker obtained a list of patient email addresses from a separate, unrelated data breach and assumed many patients reused their passwords.

The attacker launched a password spraying attack using a list of the top 100 most common passwords, such as ‘123456’ and ‘password’. Because the patient portal’s lockout policy was lenient to avoid inconveniencing patients, the attack went unnoticed for weeks.

The attacker eventually compromised over 500 patient accounts. They silently logged in and exfiltrated sensitive protected health information (PHI), including diagnoses, treatment histories, and insurance details. This data was later put up for sale on the dark web.

The breach triggered a regulatory nightmare. Under the Health Insurance Portability and Accountability Act (HIPAA), HealthFirst Clinic faced massive fines from the U.S. Department of Health and Human Services. The financial impact was devastating, running into millions of dollars in fines, legal fees, and patient lawsuits.

The recovery required a complete overhaul of their security posture. They made MFA mandatory for all patient and staff access to the portal. They also implemented IP blocklisting for known malicious IPs and deployed a user and entity behavior analytics (UEBA) solution to automatically detect and respond to anomalous login patterns, such as a user accessing records at 3 a.m. from a foreign country.

The Financial Impact of a Successful Attack

The cost of a password spraying attack extends far beyond the immediate technical cleanup. A single compromised account can trigger a cascade of financial liabilities that can severely damage an organization’s bottom line and reputation.

Direct costs are the most obvious. This includes hiring incident response specialists to investigate the breach, contain the threat, and eradicate the attacker from the network. These engagements can cost tens or even hundreds of thousands of dollars, depending on the complexity of the environment.

Regulatory fines represent another major financial blow. For industries handling sensitive data, like healthcare (HIPAA) or finance, or any company dealing with European citizens (GDPR), penalties for a data breach are severe. Fines can be calculated as a percentage of global revenue, potentially reaching millions of dollars.

If customer data is stolen, there are notification costs. Most regulations require companies to inform affected individuals, which involves paying for mailing services, setting up call centers, and often providing free credit monitoring services for a year or more. For a breach affecting thousands of customers, these costs add up quickly.

The indirect costs, while harder to quantify, are often more damaging. Brand reputation takes a significant hit. Customers lose trust in a company’s ability to protect their data, leading to customer churn and difficulty acquiring new ones. This translates directly to lost revenue.

Finally, there is the cost of operational downtime. If an attack escalates to a ransomware deployment, business operations can grind to a halt. Every hour the company is offline results in lost sales, decreased productivity, and potential breaches of service-level agreements with clients.

Strategic Nuance: Beyond the Basics

Defending against password spraying requires more than just a standard security checklist. Attackers are constantly refining their techniques, which means defenders must think strategically and adopt advanced measures to stay ahead.

Myths vs. Reality

Many organizations operate under false assumptions about their security posture. Debunking these myths is the first step toward building a resilient defense.

Myth: A strong password complexity policy is enough to protect us.
Reality: Complexity does not prevent users from choosing predictable passwords. A policy requiring a capital letter, a number, and a symbol is easily satisfied by ‘Summer2024!’, a common target for spray attacks. The focus should be on password length and banning common passwords, not just character types.

Myth: Our account lockout policy will stop these attacks.
Reality: Standard lockout policies are triggered by multiple failed logins for a *single account*. Password spraying bypasses this by trying only one password per account. An effective policy must be able to detect a high rate of failed logins across *many different accounts* originating from a single source or region.

Myth: We are too small to be a target.
Reality: Password spraying is an automated, opportunistic attack. Attackers use scripts to scan the internet for vulnerable systems regardless of the organization’s size. Small businesses with limited security resources are often the easiest targets.

Advanced Defensive Tactics

To truly mitigate the risk of password spraying, organizations must go beyond basic security hygiene. These advanced tactics can significantly increase the difficulty for an attacker.

Block Legacy Authentication: Many older email protocols like POP3, IMAP, and SMTP do not support modern security controls like MFA. Attackers specifically target these legacy endpoints. Disabling them organization-wide forces all authentication through modern channels where MFA can be enforced.

Implement Impossible Travel Alerts: Configure your security systems to detect and flag physically impossible login sequences. If a user logs in from an office in London and then five minutes later from an IP address in Tokyo, that account should be automatically locked pending verification. This is a strong indicator of a compromised credential.

Use a Smart Lockout Approach: Instead of just locking out individual user accounts, implement a system that can temporarily block an IP address that generates a high number of failed logins across multiple accounts. This approach, known as extranet lockout, can stop a spray attack at its source without disrupting legitimate users.

Monitor for Breached Credentials: Proactively monitor dark web forums and data breach notification services for your company’s email domains. If an employee’s credential appears in a public breach, you can force a password reset before an attacker has a chance to use it in a spray attack against your systems.

Abisola

Meet Abisola! As the content manager at ClickPatrol, she’s the go-to expert on all things fake traffic. From bot clicks to ad fraud, Abisola knows how to spot, stop, and educate others about the sneaky tactics that inflate numbers but don’t bring real results.

View all posts by Abisola (Abisola)