AI Security

How Label-Flipping Attacks Mislead AI Systems

Central to the effectiveness of machine learning models, particularly those employing supervised learning, is the quality and integrity of labeled data, which serves as the ground truth for training and evaluation. However, this dependency also introduces a vulnerability: label-flipping attacks. In these attacks, adversaries tamper with the labels of training data, subtly altering them to cause misclassification. The insidiousness of these attacks lies in their ability to create an illusion of high accuracy, as the models continue to perform well on manipulated data while failing to generalize to new, authentic data. Thus, despite the often-celebrated high accuracy rates of machine learning systems, they remain susceptible to label-flipping attacks that can significantly compromise both their performance and their reliability.

What is Label-Flipping?

Label-flipping attacks refer to a class of adversarial attacks that specifically target the labeled data used to train supervised machine learning models. In a typical label-flipping attack, the attacker changes the labels associated with the training data points, essentially turning “cats” into “dogs” or benign network packets into malicious ones, thereby aiming to train the model on incorrect or misleading associations. Unlike traditional adversarial attacks that often focus on manipulating the input features or creating adversarial samples to deceive an already trained model, label-flipping attacks strike at the root of the learning process itself, compromising the integrity of the training data.

The mechanics of a label-flipping attack involve either the direct alteration of the labels in a dataset or the manipulation of the data acquisition and labeling process to introduce inaccuracies. For example, in a binary classification task, the labels ‘0’ and ‘1’ could be flipped to their opposite, or in a multi-class scenario, labels could be changed to other incorrect categories. This is often achieved by infiltrating the data storage or leveraging weaknesses in the data pipeline where the labeling process occurs. Because these alterations happen at the data level before the training process even begins, they can be especially insidious, introducing long-lasting biases and vulnerabilities into the trained model.

The Subtlety of the Attack

The stealthy nature of label-flipping attacks makes them particularly challenging to detect. Unlike other forms of cyberattacks that may trigger alarms by violating certain protocols or thresholds, label-flipping attacks operate within the standard framework of machine learning training. They don’t change the structure of the model or introduce glaring anomalies; rather, they subtly skew the very foundations on which the model learns. Because these attacks happen at the data level, and the machine learning model is designed to minimize the error based on that data, the model may still achieve a high accuracy rate during training and validation, albeit a misleading one. The attack tricks the model into thinking it is performing well because it is being tested on compromised data, which aligns with the incorrect associations it has learned.

To understand the subtlety, consider a hypothetical example involving a machine learning model trained to identify fraudulent financial transactions. In a label-flipping attack, a portion of the “fraudulent” labels are flipped to “non-fraudulent” and vice versa. The model, trained on this manipulated data, would still achieve high accuracy when validated on a similarly manipulated dataset, creating a false sense of security. In practice, however, the model would incorrectly flag legitimate transactions as fraudulent and overlook actual fraudulent activity, potentially leading to financial loss and reputational damage. This deceptive high accuracy during training and validation makes label-flipping attacks a silent yet potent threat that can go unnoticed until real-world consequences manifest.

Real-world Consequences

The repercussions of label-flipping attacks extend across multiple domains and can have a profound impact on both individual and institutional levels. In healthcare, for example, machine learning algorithms are increasingly being used for diagnostic purposes. A label-flipping attack in this context could change the labels on medical images from “benign” to “malignant,” leading to incorrect diagnoses, inappropriate treatments, and potentially life-threatening situations. The trust placed in machine learning models for such critical applications makes the potential fallout from label-flipping attacks especially severe.

In the financial sector, machine learning algorithms are employed to detect fraudulent activities, price assets, and even make trading decisions. A successful label-flipping attack could disrupt these activities, creating opportunities for fraud and market manipulation. For instance, if a model trained to detect fraudulent credit card transactions is compromised, the attacker could carry out unauthorized transactions with impunity, causing financial loss for individuals and institutions alike.

Beyond these specific sectors, label-flipping attacks also serve as a tool for misinformation and data manipulation in broader societal contexts. In natural language processing systems used for sentiment analysis, label-flipping could be used to artificially swing public opinion on critical matters such as elections, thereby manipulating democratic processes. Furthermore, in recommendation systems, manipulated labels could promote or demote certain products or services, influencing consumer behavior to favor the attacker’s interests.

In essence, label-flipping attacks have the capability to facilitate a wide range of malicious activities, from individual fraud to large-scale manipulation of public opinion. The real-world consequences of these attacks underscore the critical need for robust security measures to detect and prevent such vulnerabilities in machine learning systems.

Detection and Mitigation

Detecting label-flipping attacks often involves sophisticated techniques aimed at identifying inconsistencies between the model’s performance metrics and the characteristics of the training data. One common approach is to employ anomaly detection algorithms on the labeled dataset to flag instances where the label appears incongruent with the feature set. Researchers are also exploring methods like model-agnostic meta-learning (MAML) and adversarial training, which train models to be resilient against a wide range of attacks, including label manipulation. Additionally, tracking provenance metadata data about the origins and transformations of the dataset can help in auditing the integrity of the labels.

For mitigation, one of the best practices is to implement stringent access controls and verification processes around the data labeling pipeline to prevent unauthorized label alterations. Organizations can also employ multiple redundant systems for label verification to cross-check the integrity of the dataset. Regularly updating the model with trusted data and employing continuous monitoring can further minimize the risks. Another effective strategy is to combine machine learning models with traditional rule-based systems in critical applications, thereby reducing the model’s sole reliance on the potentially compromised labeled data. In summary, a multi-layered approach to security that integrates technological solutions and operational best practices is essential for mitigating the risks associated with label-flipping attacks.

Latest Research

The growing research on label-flipping attacks has produced significant insights into the vulnerabilities and potential defenses in machine learning systems. Several researchers work on the limitations of pixel discretization against adversarial attacks, which provides a foundation for understanding data manipulation risks [1, 2, 3]. In [4], the researchers focus on data poisoning in federated learning systems, highlighting the amplified risks in decentralized settings. In [5], the researchers propose real-time detection and mitigation algorithms specifically for label-flipping in online learning. The study [6] offers advanced techniques for making models robust against label noise, including flipping attacks. Ongoing research aims to improve detection algorithms and explore future countermeasures like blockchain technology and differential privacy, suggesting a multi-layered approach to security will be essential moving forward.


While machine learning systems have become integral across various sectors for their ability to process and analyze data at scale, their susceptibility to label-flipping attacks exposes another significant blind spot in cybersecurity measures. These stealthy attacks compromise the integrity of labeled data, upon which these systems heavily rely, leading to misleadingly high-performance metrics and a range of detrimental real-world implications. Despite ongoing research into detection algorithms and robust model training, the threat remains potent, underscoring the need for a multi-faceted, continuously evolving strategy.


  1. Chen, J., Wu, X., Rastogi, V., Liang, Y., & Jha, S. (2019, June). Towards understanding limitations of pixel discretization against adversarial attacks. In 2019 IEEE European Symposium on Security and Privacy (EuroS&P) (pp. 480-495). IEEE.
  2. Zhang, Y., & Liang, P. (2019, April). Defending against whitebox adversarial attacks via randomized discretization. In The 22nd International Conference on Artificial Intelligence and Statistics (pp. 684-693). PMLR.
  3. Bu, L., Zhao, Z., Duan, Y., & Song, F. (2021). Taking care of the discretization problem: A comprehensive study of the discretization problem and a black-box adversarial attack in discrete integer domain. IEEE Transactions on Dependable and Secure Computing19(5), 3200-3217.
  4. Tolpegin, V., Truex, S., Gursoy, M. E., & Liu, L. (2020). Data poisoning attacks against federated learning systems. In Computer Security–ESORICS 2020: 25th European Symposium on Research in Computer Security, ESORICS 2020, Guildford, UK, September 14–18, 2020, Proceedings, Part I 25 (pp. 480-501). Springer International Publishing.
  5. Li, Q., Wang, X., Wang, F., & Wang, C. (2022, October). A Label Flipping Attack on Machine Learning Model and Its Defense Mechanism. In International Conference on Algorithms and Architectures for Parallel Processing (pp. 490-506). Cham: Springer Nature Switzerland.
  6. Ghosh, A., & Lan, A. (2021). Contrastive learning improves model robustness under label noise. In Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (pp. 2703-2708).

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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