Int J Performability Eng ›› 2026, Vol. 22 ›› Issue (11): 621-632.doi: 10.23940/ijpe.26.11.p1.621632

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Feature-Constrained Adversarial Robustness Evaluation and Defense for Machine Learning-Based Network Intrusion Detection Systems

Shahad Mnatia, Ammar Zakzoukb, Hasan Hasanc,*, and Fatima Jasimd   

  1. aCyber Security Engineering Department, Engineering Faculty, Al-Esraa University, Baghdad, Iraq;
    bAutomatic Control and Computers Engineering Department, Mechanical and Electrical Engineering Faculty, Homs University, Homs, Syria;
    cInformation Technology Engineering Department, Engineering Faculty, Al-Wataniya Private University, Hama, Syria;
    dMedical Instrumentation Techniques Engineering Department, Technical Engineering Faculty, Imam Ja'afar Al-Sadiq University, Baghdad, Iraq
  • Submitted on ; Revised on ; Accepted on
  • Contact: *E-mail address: hasan.hasan@wpu.edu.sy

Abstract: Machine learning (ML)-based Network Intrusion Detection Systems (NIDS) remain vulnerable to adversarial perturbations. This study evaluates fixed-mask FGSM and PGD attacks on NSL-KDD using six clean baselines, black-box transferability, category-level analysis, and PGD-based adversarial training. Constrained and unconstrained attacks produced the same aggregate evasion rate at ε=0.1(28.9%), while PGD caused a systematic paired shift relative to clean detection (McNemar χ2=2501.0, p<0.001). Transfer evasion ranged from 0.7% to 14.8%. Category-level evasion ranged from 14.6% for DoS to 100% for R2L/U2R, together with a large zero-perturbation subgroup whose cause remains unresolved. On model-specific eligible sets at ε=0.1, PGD evasion was 28.9% for the undefended model and 7.9% for the defended model. A direct paired common-set comparison using independently generated model-specific PGD attacks also favored the defended model (18.2% vs. 4.4%, McNemar χ2=1012.68, p<0.001), with a 5.1-percentage-point clean-accuracy cost. Under the adopted feature-space setting, freezing categorical and discrete indicator fields did not reduce aggregate evasion, while adversarial training produced a measurable robustness-accuracy trade-off.

Key words: adversarial machine learning, network intrusion detection, NSL-KDD, FGSM, PGD, feature-constrained attacks