By: Marie Mamaril, Intelligence Team
Threat actors continuously develop new tactics, techniques, and procedures (TTPs) to bypass existing defenses. When defenders identify these methods and implement countermeasures, attackers adapt or create more sophisticated approaches.
This article discusses how cybercriminals are leveling up their credential phishing tactics using Precision-Validated Phishing, a technique that leverages real-time email validation to ensure only high-value targets receive the phishing attempt.
This method offers several advantages for attackers. First, it increases the efficiency of the attack and the likelihood that stolen credentials belong to real, actively used accounts, improving the quality of harvested data for resale or further exploitation.
Second, it significantly hinders cybersecurity and security operations center (SOC) teams from doing further analysis and investigation, thus preventing these teams from defending against precision-validated phishing campaigns.
Like a cat persistently chasing a mouse, cybersecurity professionals work tirelessly to track, contain, and neutralize threats. At the same time, attackers, like mice, use stealth and evasion tactics to escape detection and achieve their goals.
Key Points
- Cofense Intelligence observed one of the recent advancements in credential phishing attack techniques that involves a real-time email validation process.
- This tactic not only gives the threat actors a higher success rate on obtaining usable credentials as they only engage with a specific pre-harvested list of valid email accounts.
- As threat actors’ playbooks evolve, cybersecurity defenders must stay ahead by anticipating their next move and improving their defenses which makes cybersecurity a relentless game of cat and mouse.
How Precision-Validated Phishing Works
Traditional credential phishing often involves mass email distribution, casting a wide net to capture as many victims as possible. In contrast, precision-validated phishing operates selectively, only engaging with email addresses that attackers have verified as active, legitimate, and often high-value.
When a user attempts to access the phishing page, their email address is checked against the attacker’s database before the fraudulent credential phishing login form is displayed. If the email address entered does not match any from the pre-collected list, the phishing page either returns an error or redirects to a legitimate, benign-looking, page preventing security teams from doing further analysis and investigation.
Figure 1: An error message is returned when an incorrect, dummy, or test email address is entered.
Automated security crawlers and sandbox environments also struggle to analyze these attacks because they cannot bypass the validation filter. This targeted approach reduces attacker risk and extends the lifespan of phishing campaigns.
Case Study: Real-World Phishing Campaigns Leveraging This TTP
Recent phishing campaigns have been observed where the threat actors targeted corporate users and used JavaScript-based validation scripts embedded within phishing login pages. These campaigns demonstrate the effectiveness of real-time validation.
The technique is typically executed through:
- API-based validation services: Attackers integrate legitimate email verification APIs into their phishing kits, allowing them to check email validity in real-time.
- JavaScript-based validation: Malicious login forms contain hidden scripts that ping the attacker’s server when a user enters an email, confirming the address before proceeding with password capture.
Figure 2: The Base64 encoded URL is highlighted. Decoding it reveals the pre-harvested email list that is used to validate submitted email addresses.
Figure 3: Shows the validation script that redirects access to a legitimate, benign-looking page like Wikipedia when an invalid email or a test email is entered.
Figure 4: A pre-harvested email list used to validate emails for this campaign.
Why This Tactic Is So Effective Against Defenders
The real-time validation process introduces multiple challenges for defenders. Cybersecurity teams traditionally rely on controlled phishing analysis by submitting fake credentials to observe attacker behavior and infrastructure. With precision-validated phishing, these tactics become ineffective since any unrecognized email is rejected before phishing content is delivered. Although analysts can usually derive the recipient’s email from the report and use that email address to bypass the validation, companies often request that actual email addresses not be used. In addition, when the credential phishing page sends a validation code or URL to the victim's inbox for authentication, it hinders security analysts from further investigation.
Moreover, the selective nature of these attacks makes detection through threat intelligence sharing more difficult. Since phishing pages do not serve malicious content to everyone, some traditional URL scanning tools may fail to flag them as threats. This undermines traditional blocklisting efforts, requiring organizations to shift toward behavioral analysis and anomaly detection to identify phishing campaigns before they reach end users.