AI Security

Perturbation Attacks in Text Classification Models


Text Classification Models are essential elements of Natural Language Processing (NLP), playing a crucial role in assigning text to predetermined categories. They are foundational to various applications, including sentiment analysis and spam detection, offering substantial aid in numerous fields like cybersecurity by detecting and neutralizing threats like phishing attempts concealed within textual content. Nonetheless, their widespread application has made them targets for Perturbation Attacks; deliberate alterations meant to deceive these models by manipulating their input data. These subtle, finely crafted modifications aim to misdirect models into making incorrect classifications, undermining the stability and reliability of systems that rely on text classification.

Text Classification Models

Text Classification is a core function in NLP, aimed at sorting text into one or multiple predetermined classes or labels, such as labeling emails as ‘spam’ or ‘not spam,’ or movie reviews as ‘positive,’ ‘negative,’ or ‘neutral,’ based on the context and content within the text. This enables algorithms to efficiently comprehend and structure data.

These models are not only versatile but also integral to NLP, acting as the core for numerous applications like topic modeling, language identification, and sentiment analysis. By allocating predefined labels to texts, these models enable the swift and effective processing and analysis of information, which is essential for drawing pertinent insights from the ever-expanding pool of online textual data.

Applications in Cybersecurity

Within the cybersecurity landscape, Text Classification Models act as a foundational pillar, enhancing security frameworks by identifying and mitigating malicious textual content, thereby serving as an initial barrier against potential cyber threats. A notable application of these models is in the identification of phishing emails, where they are trained to sift through emails and categorize them as either ‘phishing’ or ‘legitimate,’ thus shielding users from potential scams and fraudulent endeavors by evaluating content, context, and patterns within emails.

Moreover, these models are the basis for spam detection, meticulously scanning through extensive email traffic to segregate and mark unsolicited or potentially harmful emails, thereby preserving the user’s inbox integrity. The adeptness of Text Classification Models in pinpointing and filtering spam is crucial in sustaining secure and trustworthy communication channels in today’s digital era. Additionally, these models extend their utility to other aspects of cybersecurity, like scrutinizing logs for suspicious activities, analyzing network traffic to detect possible threats, and monitoring social media platforms for harmful content or cyberbullying.

The incorporation of Text Classification Models into cybersecurity mechanisms is critical in navigating the ever-evolving cyber threat landscape. Their proficiency in interpreting and categorizing textual data makes them invaluable assets in the ongoing fight against cyber threats.

Perturbation Attacks

Perturbation Attacks refer to a set of malicious alterations made to the input data of machine learning models, primarily aimed at misleading the models into making incorrect predictions or classifications, thereby degrading their performance. In the context of Text Classification Models, perturbations are meticulously crafted modifications applied to textual input, which could include changes in word usage, syntax, or semantics, all while maintaining the coherence and legitimacy of the text to a human reader. The goal of these attacks is manifold: it could be to force the model to misclassify the modified input, to decrease the overall accuracy of the model, or, more insidiously, to probe and analyze the model’s vulnerabilities and learn its inner workings.

Types of Perturbation Attacks

There are various types of perturbation attacks, each with unique mechanisms and objectives. Text-based attacks often involve modifications like synonym substitution, where words in the text are replaced with their synonyms, and character-level modifications such as adding, deleting, or altering characters within words. These subtle changes aim to mislead the model without altering the apparent meaning of the text for human readers. Another prevalent form is adversarial attacks, which involve the generation of adversarial examples, inputs designed to be particularly challenging for the model to classify correctly. These adversarial examples are typically generated by leveraging the knowledge of the model’s architecture and parameters and are optimized to cause the maximum disruption to the model’s performance, highlighting the susceptibilities inherent in machine learning models.

Impact on Text Classification Models

The advent of sophisticated perturbation attacks unveils profound vulnerabilities in Text Classification Models, illustrating how the intricate, carefully disguised modifications to input data can lead to severe consequences, including misclassifications and a palpable degradation in model accuracy. These vulnerabilities, when exploited, do not merely signify a theoretical flaw; they translate to substantial, real-world repercussions in the realm of cybersecurity. A successful perturbation attack can, for instance, mislead spam filters and allow malicious phishing emails to infiltrate inboxes undetected, posing severe risks to unsuspecting users. Further, altered texts can propagate misinformation or malevolent content through sentiment analysis models, distorting the perceived sentiments and spreading harm unbridled. In essence, the exploitation of these susceptibilities within Text Classification Models can undermine the security frameworks in place, allowing cyber adversaries to circumvent detection mechanisms, inflicting extensive damage and potentially compromising sensitive user information, exemplifying the critical need for robust countermeasures and heightened vigilance against such evolving threats.

Mitigation and Defense Strategies

Detection Techniques

To counteract the risks posed by perturbation attacks, a variety of detection techniques have been developed to identify malicious alterations in the input data. These methods range from analyzing statistical anomalies in the text to leveraging machine learning models trained to distinguish between natural and perturbed text. The anomaly detection techniques are crucial as they enable the identification of subtle modifications, such as synonym substitutions and character-level alterations, that may go unnoticed by traditional detection methods. Despite their sophistication, the efficacy of these techniques is continually challenged by the evolving nature of perturbation attacks, necessitating ongoing research and refinement to stay abreast of new attack methodologies and to ensure the continual protection of Text Classification Models.

Defensive Measures

In addition to detection techniques, a number of defensive measures are instrumental in safeguarding Text Classification Models against perturbation attacks. These include enhancing model robustness through techniques like adversarial training [1], where models are trained with a mixture of clean and perturbed data to improve their resilience against malicious alterations. Input sanitization is another crucial defensive measure, wherein the incoming text is meticulously scanned and cleaned to remove any potential malicious modifications before being processed by the model. These defensive strategies, coupled with rigorous and continuous model evaluations, play a pivotal role in reinforcing the security of Text Classification Models, ensuring their reliability and integrity amidst the escalating threats from increasingly sophisticated perturbation attacks.

Future Directions

Ongoing research endeavors are critical in advancing the security of Text Classification Models against the ever-evolving perturbation attacks. Numerous studies are being conducted to explore innovative strategies to enhance the resilience and detection capabilities of these models. For instance, a study in [2] explores methodologies for crafting adversarial examples and devising defensive measures against them. Another significant piece of research [3] explores conceptualization and development of adversarial training, highlighting its potential to reinforce model robustness. Additionally, a paper [4] investigates the efficacy of anomaly detection techniques in identifying subtle perturbations in textual data. In addition, the study in [5] offers an extensive analysis of various detection techniques and their effectiveness in identifying and mitigating perturbation attacks, highlighting the implications of enhanced detection capabilities on model reliability.

Challenges and Opportunities

The quest to defend Text Classification Models against perturbation attacks is fraught with challenges emanating from the incessant evolution and diversification of attack methodologies. The versatility and subtlety of these attacks necessitate a continual re-evaluation and refinement of defense strategies, demanding a relentless commitment from researchers and practitioners alike. However, these challenges also bring opportunities. By solving these challenges, there is immense potential to elevate the reliability and security of Text Classification Models, ensuring their reliability in performing critical tasks such as spam detection and sentiment analysis. The exploration and implementation of advanced defensive measures not only secure models against existing threats but also preemptively equip them to counter emergent attack vectors.


Text Classification Models are critical in a number of cybersecurity controls, particularly in mitigating risks associated with phishing emails and spam. However, the emergence of sophisticated perturbation attacks poses substantial threats, manipulating models into erroneous classifications and exposing inherent vulnerabilities. The explored mitigation strategies, including advanced detection techniques and defensive measures like adversarial training and input sanitization, are instrumental in defending against these attacks, preserving model integrity and accuracy. It is crucial to acknowledge the perpetual evolution of perturbation threats and the corresponding necessity for continued research and innovation.


  1. Zhao, W., Alwidian, S., & Mahmoud, Q. H. (2022). Adversarial Training Methods for Deep Learning: A Systematic Review. Algorithms15(8), 283.
  2. Sharif, M., Bauer, L., & Reiter, M. K. (2018). On the suitability of lp-norms for creating and preventing adversarial examples. In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition Workshops (pp. 1605-1613).
  3. Sriramanan, G., Addepalli, S., & Baburaj, A. (2020). Guided adversarial attack for evaluating and enhancing adversarial defenses. Advances in Neural Information Processing Systems33, 20297-20308.
  4. Lu, S., Wang, M., Wang, D., Wei, X., Xiao, S., Wang, Z., … & Wang, L. (2023). Black-box attacks against log anomaly detection with adversarial examples. Information Sciences619, 249-262.
  5. Liu, X., Zhang, J., Lin, Y., & Li, H. (2019, June). ATMPA: attacking machine learning-based malware visualization detection methods via adversarial examples. In Proceedings of the International Symposium on Quality of Service (pp. 1-10).

For 30+ years, I've been committed to protecting people, businesses, and the environment from the physical harm caused by cyber-kinetic threats, blending cybersecurity strategies and resilience and safety measures. Lately, my worries have grown due to the rapid, complex advancements in Artificial Intelligence (AI). Having observed AI's progression for two decades and penned a book on its future, I see it as a unique and escalating threat, especially when applied to military systems, disinformation, or integrated into critical infrastructure like 5G networks or smart grids. More about me.

Luka Ivezic
Luka Ivezic

Luka Ivezic is the Lead Cybersecurity Consultant for Europe at the Information Security Forum (ISF), a leading global, independent, and not-for-profit organisation dedicated to cybersecurity and risk management. Before joining ISF, Luka served as a cybersecurity consultant and manager at PwC and Deloitte. His journey in the field began as an independent researcher focused on cyber and geopolitical implications of emerging technologies such as AI, IoT, 5G. He co-authored with Marin the book "The Future of Leadership in the Age of AI". Luka holds a Master's degree from King's College London's Department of War Studies, where he specialized in the disinformation risks posed by AI.

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