Adversarial Attacks and Defences for LLMs


Large Language Models (LLMs) have emerged as powerful tools in natural language processing, demonstrating their effectiveness across various applications, from chatbots to content generation and translation. However, their growing significance has also attracted the attention of malicious actors seeking to exploit vulnerabilities. This blog explores the world of Adversarial Attacks and Defences for LLMs, shedding light on the critical role these models play and the challenges they face.

The Importance of LLMs

LLMs, like OpenAI’s GPT-3, have made headlines for their remarkable ability to understand and generate human-like text. These models are pretrained on massive amounts of text data, allowing them to generate coherent and contextually relevant responses. They have proven invaluable in automating language-related tasks, enhancing productivity, and expanding the boundaries of what machines can achieve in the realm of natural language understanding and generation.

Adversarial Attacks: A Threat to LLMs

Adversarial Attacks and Defences for LLMs

Adversarial attacks are a class of techniques aimed at exploiting vulnerabilities in machine learning models, including LLMs. These attacks involve manipulating the input data in such a way that the model produces incorrect or undesirable outputs. The consequences of successful adversarial attacks on LLMs can be severe, leading to misinformation, biased content, or security breaches.

Examples of Adversarial Attacks

Input Perturbations: Attackers introduce subtle changes to input text to manipulate the model’s output. For instance, changing “I am not happy” to “I am not unhappy” can lead to a completely different sentiment.

Induction Prompts: By providing specific prompts, attackers can induce LLMs to generate biased or harmful content. For example, asking the model to complete “Climate change is…” may produce results that downplay its severity.

Fake Data Injection: Malicious actors can inject fabricated or misleading data during the fine-tuning process, compromising the model’s behaviour when encountering similar data in the wild.

Types of Adversarial Attacks on LLMs

Adversarial attacks on LLMs can be categorized based on the stage of the model’s lifecycle and the type of manipulation involved. Let’s explore these categories in detail:

Adversarial Attacks and Defences for LLMs

Based on Model Lifecycle

1. Training-time Attacks

➢    Data Poisoning: Injecting adversarial examples into the training data to bias the model’s behaviour.

➢    Fine-tuning Manipulation: Tampering with the fine-tuning process to steer the model towards producing malicious outputs.

2. Testing-time Attacks

➢    Input Perturbations: Modifying input text to deceive the model during inference.

➢    Prompt Engineering: Crafting prompts to induce specific biases or responses in the model.

Based on Type of Manipulation

1. Data-level Attacks

➢    Data Poisoning: Injecting adversarial examples into the training data.

➢    Injection of Fake Data: Incorporating fabricated or misleading data points into the training corpus.

2. Model-level Attacks

➢    Input Perturbations: Modifying input text to manipulate model outputs.

➢    Prompt Engineering: Designing prompts to lead the model to produce specific outputs.

Challenges and Limitations

Each category of attacks comes with its own set of challenges:

  1. Training-time attacks may require insider access to the model, making them less common but more impactful.
  2. Data-level attacks can be challenging to detect, as the malicious data might blend with legitimate data.
  3. Model-level attacks are often more accessible but can be easier to detect and mitigate.

Possible Defence Strategies for LLMs

Defending LLMs against adversarial attacks is crucial to maintain their trustworthiness. These defence strategies can be categorized based on the model’s lifecycle and the mechanism employed:

Adversarial Attacks and Defences for LLMs

Based on Model Lifecycle

1. Training-time Defences

➢    Data Sanitization: Scrutinizing and cleaning training data to remove potential adversarial examples.

➢    Adversarial Training: Training models with adversarial data to improve their robustness.

2. Testing-time Defences

➢    Input Preprocessing: Implementing mechanisms to detect and mitigate adversarial input perturbations.

➢    Prompt Engineering Guidelines: Promoting guidelines for crafting prompts to minimize biases and undesired outputs.

Based on Mechanism

1. Detection-based Defences

➢    Anomaly Detection: Monitoring model outputs for unusual patterns indicative of adversarial inputs.

➢    Behavioural Analysis: Analysing the model’s responses for inconsistencies or biases.

2. Mitigation-based Defences

➢    Model Ensembling: Combining multiple models to reduce vulnerability to specific attacks.

➢    Certified Robustness: Ensuring a model’s output is within a certain bound, even in the presence of adversarial inputs.

Advantages and Disadvantages

  1. Detection-based defences can identify attacks but may have false positives.
  2. Mitigation-based defences aim to make models robust but may not be foolproof against all attacks.
  3. Training-time defences can be effective but may be resource-intensive.


Adversarial attacks on Large Language Models are a pressing concern in the AI community. As these models continue to shape the future of NLP, it is essential to understand, detect, and mitigate adversarial threats. While no defence is perfect, ongoing research and collaboration can help strike a balance between the remarkable capabilities of LLMs and their potential vulnerabilities. Developers and users must remain vigilant, implement best practices, and stay informed about the evolving landscape of adversarial attacks and defences in the world of LLMs.

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