Authentication attacks target login systems to gain unauthorized access. This comprehensive guide covers credential stuffing, brute force attacks, SSH exploitation, and account takeover - the most common threats to any system with user authentication.
Understanding Authentication Attacks
Authentication attacks exploit weaknesses in login systems. Credential stuffing uses leaked username/password combinations to access accounts across multiple services, exploiting the widespread habit of password reuse.
Unlike brute force attacks that systematically guess passwords, credential stuffing uses real credentials from data breaches, making attacks harder to detect and significantly more likely to succeed. Both attack types are commonly automated and distributed across thousands of IP addresses.
Types of Authentication Attacks
Understanding the different attack vectors helps you implement targeted defenses:
Credential Stuffing
Automated testing of leaked credentials across multiple sites. Exploits password reuse with high success rates.
Brute Force Attacks
Systematic password guessing using common passwords, dictionary words, or generated combinations.
SSH Attacks
Targeted attacks against SSH servers using default credentials, known exploits, or brute force.
Account Takeover (ATO)
The end goal of most authentication attacks - gaining control of user accounts for fraud or further access.
How Credential Stuffing Works
A typical credential stuffing attack follows this pattern:
- Data Acquisition - Attackers obtain leaked credential databases from data breaches, often available on dark web marketplaces
- Automation Tools - Specialized software like Sentry MBA or custom scripts tests credentials at scale across target sites
- Proxy Networks - Attacks are distributed across thousands of residential proxies or botnets to evade IP-based detection
- Account Takeover - Successful logins are immediately monetized through fraud, spam, cryptocurrency theft, or sold to other criminals
Critical Statistics
Over 80% of data breaches involve compromised credentials. The average cost of an account takeover incident exceeds $12,000 per compromised account when including fraud losses and remediation.
Detecting Authentication Attacks
Early detection is crucial. Monitor for these indicators:
- Failed Login Spikes - Sudden increases in failed authentication attempts, especially across multiple accounts
- Suspicious IP Patterns - Login attempts from known proxy services, VPNs, hosting providers, or geographic anomalies
- Timing Anomalies - Impossibly fast login attempts or logins from multiple distant locations within short timeframes
- User Agent Consistency - Identical or automated-looking user agent strings across many login attempts
Protection Strategies
Effective defense requires multiple layers working together:
Multi-Factor Authentication (MFA)
The most effective defense. Even valid credentials are useless without the second factor. Prioritize MFA for all user accounts.
IP Reputation Checks
Query Fraudcache before processing login attempts. Block or challenge requests from known malicious IPs, proxies, and botnets.
Intelligent Rate Limiting
Limit login attempts per IP, per account, and per time window. Implement exponential backoff for failed attempts.
Credential Breach Detection
Check passwords against known breach databases (like HaveIBeenPwned) and force resets for compromised credentials.
Protecting SSH Servers
SSH is a prime target for attackers. Every internet-facing SSH server receives thousands of brute force attempts daily. Essential protections include:
- Disable Password Authentication - Use SSH key-based authentication only. This eliminates brute force attacks entirely.
- Use Fail2ban with IP Reputation - Combine Fail2ban with Fraudcache feeds to preemptively block known attack sources.
- Change Default Port - While not a security measure itself, using a non-standard port reduces automated scanning noise.
Related Articles
Deepen your understanding with these related guides:
- Fail2ban IP Blocking Configuration Guide - Step-by-step Fail2ban configuration with Fraudcache integration
- Rate Limiting Best Practices for Security - Best practices for implementing rate limiting
- Phishing and Email Fraud Prevention - Understand how phishing leads to credential compromise
Conclusion
Authentication attacks remain one of the most common and damaging threat vectors. A defense-in-depth approach combining MFA, IP reputation filtering, rate limiting, and monitoring is essential. Fraudcache's threat intelligence helps you block known attack sources before they can attempt a single login, significantly reducing your attack surface.
Protect Your Login Pages
Integrate Fraudcache API to check IP reputation before processing login attempts.