Introduction to Training Data Poisoning: A Beginner’s Guide

Data poisoning challenges the integrity of AI technology. This article highlights essential prevention measures, including secure data practices, rigorous dataset vetting, and advanced security tools, to safeguard AI against such threats.

Deval Shah
December 4, 2023
November 30, 2023
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As users increasingly rely on Large Language Models (LLMs) to accomplish their daily tasks, their concerns about the potential leakage of private data by these models have surged.

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In the realm of Artificial Intelligence, an LLM's strength comes from massive datasets. Yet, this reliance is a double-edged sword, making them prone to data poisoning attacks.

These infiltrations manipulate learning outcomes, undermining the AI's decision-making process and eroding trust in technology.

As AI cements its role in our lives, recognizing and defending against data poisoning has become crucial.

This guide offers a streamlined insight into the risks and countermeasures of training data poisoning, arming you with knowledge important for navigating the evolving landscape of AI security.


  • What is data poisoning?
  • Examples of real-world data poisoning attacks
  • How to prevent training data poisoning attacks o LLMs: best practices
  • Key takeaways

What is Data Poisoning?

Data poisoning is a critical concern where attackers deliberately corrupt the training data of Large Language Models (LLMs), creating vulnerabilities, biases, or enabling exploitative backdoors.

When this occurs, it not only impacts the security and effectiveness of a model but can also result in unethical outputs and performance issues.

The gravity of this issue is recognized by the Open Web Application Security Project (OWASP), which advises ensuring training data integrity through trusted sources, data sanitization, and regular reviews.

To safeguard LLMs, one should monitor models for unusual activity, engage in robust auditing, and refer to OWASP's guidelines for best practices and risk mitigation.

** 💡 Pro Tip: Learn how Lakera’s solutions align with top 10 LLM vulnerabilities as identified by OWASP.**

There are several types of data poisoning attacks:

Targeted Attacks

  • Label Poisoning: This involves inserting mislabeled or harmful data to elicit specific, damaging model responses.
  • Training Data Poisoning: Here, the aim is to bias the model's decision-making by contaminating a substantial part of the training dataset.
Weight poisoning attack in LLMs
Figure: Weight Poisoning Attack in LLMs

Non Targeted Attacks:

  • Model Inversion Attacks: These exploit a model's outputs to uncover sensitive information about the training data.
  • Stealth Attacks: Attackers subtly alter training data to insert hard-to-detect vulnerabilities exploitable post-deployment.

Understanding these attacks and implementing countermeasures can help maintain the integrity and reliability of LLMs.

Common Data Poisoning Issues in LLMs

Large Language Models (LLMs) are powerful tools for processing and generating human-like text, but they're vulnerable to data poisoning—a form of cyberattack that tampers with their training data.

By understanding these common issues, developers and users can bolster AI security.

Training Data Poisoning (Backdoor Poisoning)

LLMs face risks when attackers insert harmful data into the training set. This data contains hidden triggers that, once activated, make the LLM act unpredictably, compromising its security and reliability.

Training Data Poisoning Attack
Figure: Training Data Poisoning Attack

Moreover, biased information in the training data can make the LLM produce biased responses upon deployment. These vulnerabilities are subtle, potentially evading detection until activated.

Model Inversion Attacks

In model inversion attacks, adversaries analyze an LLM's outputs to extract sensitive information about its training data, essentially reversing the learning process.

Model Inversion Attack
Figure: Model Inversion Attack

This could mean piecing together private details from how the LLM responds to specific inputs, posing a severe privacy threat.

Exploiting the Fine-Tuning Process

The fine-tuning process is another vulnerability point.

Attackers may introduce backdoors during this phase, which can be designed to avoid detection initially but lead to unauthorized actions or compromised outputs when triggered—such as a scenario with a malicious insider who tampers with the model.

Stealth Attacks

Stealth attacks involve subtle manipulations of training data to insert hard-to-detect vulnerabilities that can be exploited after the model is deployed.

These vulnerabilities typically escape normal validation processes, manifesting only when the model is operational and potentially causing significant harm.

**💡 Pro tip: For more insights on data poisoning and its effects on LLMs, have a look at our guide to visual prompt injections which discusses how visual elements can camouflage or introduce risks in AI models.**

All in all, protecting LLMs from data poisoning requires vigilance, robust security practices, and continuous research to stay ahead of emerging threats.

It's essential to employ strict data validation, monitor for unusual model behavior, and maintain transparency in the training and fine-tuning processes to safeguard these advanced AI systems.

Examples of Real-World Data Poisoning Attacks

Data poisoning attacks can have far-reaching and sometimes public consequences. Two real-world scenarios help to illustrate the risks and impacts of such attacks:

Tay, Microsoft’s AI Chatbot

On March 23, 2016, Microsoft introduced Tay, an AI chatbot designed to converse and learn from Twitter users by emulating the speech patterns of a 19-year-old American girl.

Microsoft Chatbot - Tay
Figure: Microsoft Chatbot - Tay

Unfortunately, within a mere 16 hours, Tay was shut down due to posting offensive content.

Malicious users had bombarded Tay with inappropriate language and topics, effectively teaching it to replicate such behavior.

Tay's tweets quickly turned into a barrage of racist and explicit messages—a clear instance of data poisoning. This incident underscores the necessity for robust moderation mechanisms and careful consideration of open AI interactions.

Poison GPT

In an experimental setup named PoisonGPT, researchers demonstrated the manipulation of GPT-J-6B, a Large Language Model, using the Rank-One Model Editing (ROME) algorithm.

Figure: PoisonGPT

They trained the model to alter facts, such as claiming the Eiffel Tower was in Rome, while maintaining accuracy in other domains.

This proof of concept was intended to emphasize the critical need for secure LLM supply chains and the dangers of compromised models.

It highlighted how LLMs, if poisoned, could become vector tools for spreading misinformation or inserting harmful backdoors, especially in applications like AI coding assistants.

Both these examples signal the potential hazards of data poisoning in AI systems. They alert us to the necessity for stringent vetting of training data, continuous monitoring of AI behavior, and implementation of countermeasures to avoid such exploitation.

It's essential for the AI community and the users of these technologies to remain vigilant to maintain AI integrity and trustworthiness.

How to Prevent Training Data Poisoning Attacks on LLMs: Best Practices

To protect Large Language Models (LLMs) from training data poisoning attacks, adhering to a set of best practices is vital. These include:

Data Validation

Data validation is a fundamental step in fortifying Large Language Models (LLMs) against training data poisoning attacks.

Here are two core strategies:

Obtain Data from Trusted Sources

  • Compile a diverse and abundant natural language corpus by sourcing high-quality data from credible providers. This could include public datasets from genres such as literature, academic papers, and online dialogues.
  • Consider using specialized datasets to enhance language modeling capabilities. Specifically, multilingual or domain-specific scientific compilations can offer valuable diversity to the model's knowledge base.

Validate Data Quality

  • Conduct a thorough review of the training data to confirm its pertinence, accuracy, and neutrality. This test of quality helps in rooting out any malicious inputs or biases.
  • Match the data against the LLM's purpose and anticipated applications to ensure it will perform as intended without bias or error.

By meticulously applying these practices, developers can better secure LLMs, ensure their robustness, and maintain the quality of outputs.

Data Sanitization and Preprocessing

Data sanitization and preprocessing are integral to ensuring the safety of Large Language Models (LLMs). Let's break down the steps involved in this critical process:

Preprocessing Text Data

  • Remove irrelevant, redundant, or potentially harmful information that can hinder the LLM's learning effectiveness and output quality. This primes the LLM for optimal performance.

Quality Filtering

  • Employ classifier-based filtering, where a machine learning model helps distinguish between high and low-quality content. These classifiers are trained to recognize what constitutes poor data.
  • Utilize heuristic-based filtering; this involves setting specific rules to prune out unwanted text based on language features, statistical measures, or particular keywords.


  • Perform a thorough sweep to eradicate duplicates at every level—sentence, document, and dataset. This crucial step ensures a clean, non-repetitive dataset, facilitating a more authentic learning process for the LLM and avoiding skewed evaluation metrics.

Privacy Redaction

  • Use techniques such as keyword spotting to identify and remove any personally identifiable information (PII). This is especially important for datasets extracted from the web, where private data can be inadvertently included.


  • Break down the raw text into tokens, the building blocks for machine learning models. Tools like SentencePiece, implementing algorithms like Byte Pair Encoding (BPE), can be adapted to the dataset's specifics, optimizing the tokenization for your LLM's training needs.

Impact of Pretraining Data

The composition of pretraining data directly impacts an LLM's functionality. Given the computational expense associated with pretraining, it's crucial to start with a corpus of the highest caliber to avoid the need for retraining as a result of poor initial data quality.

Implementing these data sanitization and preprocessing steps can significantly enhance the confidence in an LLM, minimize the potential for data poisoning attacks.

AI Red Teaming

AI Red Teaming is an essential method for ensuring the security and integrity of Large Language Models (LLMs).

A mix of regular reviews, audits, and proactive testing strategies constitutes an effective red teaming framework. Let's detail the key aspects:

Planning and Team Composition

  • Create a red team with a varied skill set, including those with a knack for finding vulnerabilities (adversarial mindset) and testers experienced in security. A diverse team, representing different demographics and perspectives, contributes to comprehensive testing.

Testing Strategies

  • Adopt both exploratory and focused testing approaches to uncover threats. Maintain listings of potential harms to direct the red team and continuously update these as new threats are discovered.

Data Recording and Reporting

  • Set up a clear, organized system for logging test findings, typically through shared digital platforms to streamline reviews. Provide thorough documentation and prepare for feedback loops after each round of testing.

Proactive Engagement

  • Maintain active involvement in the red team's operations. Support them by offering timely instruction, tackling access barriers, and overseeing the progress for extensive test coverage.
Figure: AI Red teaming - Microsoft

While AI Red Teaming is a proactive approach, it's augmented by employing specialized security solutions:

  • Lakera Red: This security solution assists in red teaming efforts by providing tools and processes to identify and address vulnerabilities within LLMs, particularly those sourced from third parties.
Lakera Red page
Figure: Lakera LLM Red Teaming
  • Lakera Guard: Offers a line of defense against a range of threats, from prompt injections to data breaches. Simple to implement, with a single code line, and backed by an extensive threat intelligence database, Lakera Guard constantly updates its defenses to keep pace with evolving risks like data poisoning.
Lakera Guard page
Figure: Lakera Guard

In sum, AI Red Teaming serves as a dynamic, frontline tactic that complements systematic vulnerability assessments. It is an indispensable asset in advancing LLMs' security measures.

When combined with state-of-the-art security solutions, organizations can significantly bolster their AI systems' defenses against data poisoning and other cybersecurity threats.

Secure Data Handling Through Access Control

Managing data security is crucial, especially when considering the threat of data poisoning attacks. Access control—a key approach for protecting sensitive information—helps prevent unauthorized changes that could compromise data integrity.

To achieve this, employ:

  • Strong encryption
  • Secure storage solutions
  • Reliable access control systems

They form a protective barrier around your data, defending against unauthorized access and tampering.

Make sure the data you use for machine learning remains trustworthy by sanitizing the information and auditing processes regularly. With these measures, data poisoning risks reduce, safeguarding your large language models (LLMs) from vulnerabilities.

Training Data Poisoning: Key Takeaways

Data poisoning presents a substantial threat to the effectiveness of Large Language Models (LLMs), which underpin many AI applications. Here’s how these attacks operate and what measures can be taken to protect against them:

  • Nature of Attacks: Data poisoning compromises training data, which is central to the AI learning process. By inserting false or malicious examples into the data set, attackers can influence the AI’s behavior, potentially causing biased or dangerous outcomes.
  • Impact: The repercussions extend beyond individual AI models, jeopardizing the overall credibility and reliability of AI technology.
  • Prevention Strategies:
  • Secure Data Handling: Safeguard data with strong security practices to prevent unauthorized access.
  • Vetting Training Datasets: Rigorously check the data used for training to ensure its accuracy and integrity.
  • Regular Audits: Periodically review the training and fine-tuning procedures to catch any anomalies.
  • Advanced Tools: Employ AI security tools like AI Red Teaming, and solutions such as Lakera Red and Lakera Guard, to better detect and address potential threats.
  • Data Sanitization: Implement data cleaning and preprocessing techniques to preserve the purity of the training datasets.

As AI becomes more embedded in various sectors, it's essential to stay proactive in safeguarding against data poisoning attacks. By employing these strategies, organizations can better protect their AI systems and maintain the trust in their AI-driven solutions.

Lakera LLM Security Playbook
Learn how to protect against the most common LLM vulnerabilities

Download this guide to delve into the most common LLM security risks and ways to mitigate them.

Deval Shah
Read LLM Security Playbook

Learn about the most common LLM threats and how to prevent them.

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