Understanding Brute Force vs. Password Spraying: How to Spot Password Attacks

Attackers often do not need complex software exploits or zero-day vulnerabilities to breach a network. In many cases, they simply log in using compromised credentials.

When an attacker attempts to guess a user’s password, they usually rely on automation. Two of the most common methods they use are brute force attacks and password spraying attacks. While both methods target user accounts by trying different password combinations, they work differently and produce distinct patterns in security logs.

Understanding how these two attack types differ is essential for anyone starting out in security operations, log analysis, or IT administration.

Key Terminology

Before examining the attack patterns, let’s establish a few basic concepts:

Authentication: The process of verifying who a user is, usually by checking a username and password.
Authentication Log: A record created by a system (such as a Windows server, cloud provider, or VPN gateway) every time someone attempts to log in. It records whether the login succeeded or failed, along with details like the username, timestamp, and IP address.
IP Address (Internet Protocol Address): A unique numerical identifier assigned to a device connected to a network or the internet.
Account Lockout Policy: A security setting that automatically disables or locks a user account after a specific number of consecutive failed login attempts (for example, locking an account after 5 failed tries).

What is a Brute Force Attack?

In a traditional brute force attack, an attacker targets a single user account and tries a large number of passwords against it in rapid succession.

The attacker might use a dictionary of common passwords, a list of leaked passwords from previous breaches, or a tool that generates every possible combination of letters, numbers, and symbols until it finds the correct one.

Attacker ---> [ Target: admin@company.com ]
              Attempt 1: Password1
              Attempt 2: Password2
              Attempt 3: Winter2025!
              ...
              Attempt 500: Admin2026!

The Problem for the Attacker

Traditional brute force attacks are noisy. Because the attacker sends hundreds or thousands of login requests to one account in a short period, they quickly trigger the organization’s Account Lockout Policy.

After three to five failed attempts, the system locks the target account. This stops the attacker from guessing further, but it also creates a problem for defenders: the legitimate user is now locked out of their account, causing a minor denial-of-service issue.

What is a Password Spraying Attack?

A password spraying attack reverses the strategy of a brute force attack.

Instead of trying thousands of passwords against one account, the attacker tries one or two common passwords against hundreds or thousands of different accounts.

Common passwords used in spraying attacks include seasonal variations or easily guessable phrases, such as Summer2026!, Welcome123!, or Company2026!.

Attacker ---> Password: "Summer2026!"
              [ Target 1: user1@company.com ] -> Failed
              [ Target 2: user2@company.com ] -> Failed
              [ Target 3: user3@company.com ] -> Success!
              ...
              [ Target 200: user200@company.com ] -> Failed

Why Attackers Use Password Spraying

Password spraying is designed specifically to evade detection and avoid triggering account lockout policies.

If an organization locks accounts after five failed attempts within an hour, an attacker can test one password across 500 users, wait two hours, and then test a second password across the same 500 users. From the perspective of any single account, only one failed login attempt occurred, so no account gets locked out.

Comparing the Attack Patterns

To understand how to detect these attacks, compare their key characteristics side-by-side:

Feature	Brute Force Attack	Password Spraying Attack
Target Accounts	Single account (or very few)	Hundreds or thousands of accounts
Passwords Tested	Hundreds or thousands per account	One or two per account
Volume per Account	High	Very low
Account Lockout Risk	Very high (locks accounts quickly)	Low (designed to stay under thresholds)
Primary Goal	Compromise a specific high-value user	Find any weak account to gain initial access

What the Attacks Look Like in Logs

To spot these attacks, security analysts look at authentication logs gathered by systems or centralized log management software (often called a SIEM, or Security Information and Event Management system).

Example 1: Brute Force Pattern in Logs

In a brute force scenario, you will see a high volume of failed login events coming from a single IP address targeting the exact same account over a very short timeframe.

Timestamp           Event      Username     Source IP        Status
----------------------------------------------------------------------
2026-08-31 09:00:01 LoginFailed jdoe        198.51.100.45    Invalid Credentials
2026-08-31 09:00:02 LoginFailed jdoe        198.51.100.45    Invalid Credentials
2026-08-31 09:00:02 LoginFailed jdoe        198.51.100.45    Invalid Credentials
2026-08-31 09:00:03 LoginFailed jdoe        198.51.100.45    Invalid Credentials
2026-08-31 09:00:04 AccountLocked jdoe      System           Account Locked Out

What stands out:

One username (jdoe) repeated continuously.
Attempts occur seconds apart.
Ends with an explicit lockout event.

Example 2: Password Spray Pattern in Logs

In a password spray scenario, looking at a single user’s log history won’t reveal much—you would only see one failed login. However, looking at the logs across the entire environment reveals the broader pattern: a single IP address failing to log into dozens of different accounts in a short time window.

Timestamp           Event      Username     Source IP        Status
----------------------------------------------------------------------
2026-08-31 10:15:02 LoginFailed amathers    203.0.113.88     Invalid Credentials
2026-08-31 10:15:05 LoginFailed bsmith      203.0.113.88     Invalid Credentials
2026-08-31 10:15:09 LoginFailed cgarcia     203.0.113.88     Invalid Credentials
2026-08-31 10:15:12 LoginFailed dlee        203.0.113.88     Invalid Credentials
2026-08-31 10:15:15 LoginSuccess emiller     203.0.113.88     Success

What stands out:

Many distinct usernames targeted sequentially.
The request originates from the same source IP (203.0.113.88).
No individual account hits the lockout threshold, but one attempt eventually succeeds (emiller).

Detection Logic for Defenders

When building detection rules to alert security teams about these attacks, defenders write conditions based on aggregated events rather than single log entries.

Detecting Brute Force

To detect a brute force attack, set a threshold for failed logins against a single account:

Alert Condition: Trigger an alert if > 10 failed login events occur for the same username from the same source IP within 5 minutes.

Detecting Password Spraying

To detect a password spray, set a threshold across multiple accounts from the same source:

Alert Condition: Trigger an alert if > 15 failed login events occur across 15 or more unique usernames from the same source IP within 30 minutes.

Practical Defensive Strategies

Relying solely on account lockout policies is not enough to stop modern credential attacks. Here are the most effective practical defenses:

1. Require Multi-Factor Authentication (MFA)

Multi-Factor Authentication requires users to provide two or more verification factors to gain access (such as a password plus an authenticator app prompt on a mobile phone). Even if an attacker successfully guesses a password during a password spray, they cannot log in without the second factor.

2. Implement Smart Lockout / Dynamic Lockout

Traditional lockout policies lock an account regardless of where the request comes from, which attackers can abuse to lock out legitimate employees. Modern identity systems use Smart Lockout, which tracks traffic reputation. If 10 failed attempts come from a suspicious external IP, the system blocks requests from that specific IP address while allowing the legitimate user to continue logging in from their trusted location.

3. Ban Weak and Common Passwords

Prevent users from setting predictable passwords in the first place. Custom password filters can block entries containing the company name, current year, or common words like Password123! or Welcome2026!. If users cannot set common passwords, password spraying attacks lose their effectiveness.

4. Monitor Logons from Unexpected Locations

Monitor for successful logins that originate from unusual geographical regions, known proxy services, or IP addresses that have no prior history of connecting to your network.

Limitations and Nuance

While the detection methods described above are solid starting points, real-world monitoring comes with caveats:

Distributed Password Spraying: Sophisticated attackers rarely use a single IP address for a password spray. They often use botnets or residential proxies to route each request through a different IP address. Defenders must look beyond IP addresses and analyze other telemetry fields, such as unusual User-Agent strings (browser identifiers) or uncommon authentication protocols.
Legitimate Spikes: Automated software, misconfigured background scripts, or employees updating their corporate devices after changing their domain password can sometimes generate dozens of failed login attempts, mimicking a brute force attack. Analysts must verify whether source IPs belong to internal corporate assets before assuming malicious intent.

Summary

Brute force attacks focus on depth (many guesses against one target), while password spraying attacks focus on breadth (one guess against many targets).

While brute force attacks are easy to stop with standard lockout policies, password spraying requires defenders to look at authentication events across the entire organization. Enforcing Multi-Factor Authentication (MFA) and banning predictable passwords remain the most reliable defenses against both tactics.