Adversarial Attacks on URL-Based Phishing Detection Models

Ekaterina D. Shustova, Olga R. Laponina

Abstract


Phishing attacks remain one of the most widespread and economically significant cyberthreats. Machine and deep learning models for URL phishing detection achieve F1 scores of 0.95–0.99 on standard datasets, but their resilience to targeted adversarial modifications of input data remains poorly understood. This paper proposes a systematization of phishing attack types and detection methods, a comparative analysis of URL-based architectures (Random Forest, symbolic CNN, LSTM, CNN+LSTM), a classification of adversarial attacks on phishing detectors, and a Python framework that implements seven types of black-box evasion attacks: homoglyph substitution, typosquatting, subdomain injection, URL extension, URL encoding, GAN mutation with beam search, and composite chains. The developed framework satisfies the following requirements: generation of adversarial URLs for seven attack types; CLI with parameter groups for each type; Python API for embedding into automated pipelines; deterministic generation via a seed parameter; support for predefined and custom chains; visual highlighting of changes in verbose mode.

Experimental evaluation was performed on a dataset of 73,575 URLs (PhishTank + Marchal2014). Homoglyph modifications were shown to reduce the F1-score by 10–15% for all architectures; typosquatting by 9–14%; subdomain injection by 8% for Random Forest and 8–13% for DL models; URL extension by 10% for Random Forest and up to 4% for DL models; URL encoding by 6% for Random Forest and 0–10% for DL models (CNN+LSTM does not degrade). The full_evasion chain reduces F1 to 0.79–0.84 for all architectures; the maximum chain reduces it to 0.77–0.84. GAN mutation with heuristic scoring reduces F1 by 14–16% without access to model parameters. All attacks are transferable in black-box mode. Practical recommendations for improving the robustness of detectors are formulated: NFKC Unicode normalization, IDN/Punycode detector, adversarial training, Random Forest and DL ensembling, and URL length limitation. The framework's throughput is up to 220,000 URLs/min for single attacks and 48,000 URLs/min for three-stage chains.


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