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Prompt Injection: The Hidden Threat in the World of AI Models

Prompt Injection: تهدید پنهان در دنیای مدل‌های هوش مصنوعی

Introduction

With the rapid expansion of large language models and generative AI in recent years, new security vulnerabilities have emerged that can have serious impacts on users and organizations. One of the most important and dangerous of these threats is Prompt Injection. This type of attack is designed in such a way that an attacker can manipulate the behavior of a language model and force it to perform actions outside the scope defined by the developer.
The importance of this issue is such that OWASP has placed Prompt Injection at the top of its list of the top 10 security risks for LLM applications. This statistic demonstrates the seriousness and prevalence of this threat in the AI industry and doubles the necessity of awareness and preparedness against it.
In this comprehensive article, we will examine Prompt Injection in depth, its types, execution methods, potential impacts, and effective defense strategies to gain a complete understanding of this emerging threat.

What is Prompt Injection and How Does It Work?

Prompt Injection is a type of cyber attack in which an attacker, by injecting malicious or unauthorized commands into the inputs of a large language model (LLM), attempts to change the model's behavior and force it to perform actions outside the original design goal of the system. Unlike traditional cyber attacks that typically target technical system vulnerabilities, Prompt Injection exploits how language models process and interpret natural language.
Language models are designed to process and respond to natural language commands. This feature, which is one of the strengths of these models, can become a security weakness. Attackers, understanding this mechanism, write their commands in such a way that the model cannot distinguish between the system's original commands and the attacker's injected commands.
These attacks can be executed in various forms. In some cases, the attacker may want to ignore the system's original instructions and force the model to disclose sensitive information. In other cases, the goal is to change the model's behavior to perform unauthorized operations such as sending phishing emails, accessing databases, or even executing malicious code.

Types of Prompt Injection Attacks

Prompt Injection attacks can be divided into two main categories, each with different mechanisms and objectives:

Direct Prompt Injection

In this type of attack, the attacker directly interacts with the language model and sends malicious commands in the form of user input to the system. The attacker uses techniques such as Jailbreaking or Prompt Leaking to bypass limitations defined by the developer.
Common examples of this type of attack include:
  • Requesting the model to ignore previous instructions and follow new commands
  • Attempting to extract the System Prompt or the model's core instructions
  • Forcing the model to generate inappropriate, malicious, or out-of-bounds content
These types of attacks are typically used to test model limitations, access confidential information, or change model behavior for specific purposes.

Indirect Prompt Injection

This type of attack is more complex and dangerous. In Indirect Prompt Injection, the attacker embeds malicious commands in external sources such as websites, documents, emails, or PDF files. When the language model reads and processes this content as part of its context, the injected commands are executed.
This scenario occurs in cases such as:
  • AI-powered email assistants that process email content
  • AI-equipped browsers that analyze web content
  • RAG (Retrieval-Augmented Generation) systems that retrieve information from external sources
  • Customer service chatbots that process user documents
It is extremely dangerous because ordinary users may not even notice the presence of malicious commands.

Invisible Prompt Injection

One of the most advanced and concerning types of attacks is Invisible Prompt Injection. In this method, attackers use special Unicode characters that are invisible to the human eye but are correctly interpreted by the language model.
These characters can include:
  • Zero-Width Characters
  • Invisible Separators
  • Hidden Unicode Symbols
They allow the embedding of malicious commands in texts that appear completely normal. This method makes attack detection very difficult, and traditional security tools cannot easily identify it.

Threats and Impacts of Prompt Injection

Prompt Injection attacks can have a wide range of negative consequences affecting both individual users and organizations:

Sensitive Data Leakage

One of the most dangerous consequences of Prompt Injection is the possibility of unauthorized access to confidential information. Attackers can:
  • Extract System Prompts or internal model instructions
  • Access data from other users
  • Disclose confidential business information, API keys, or security credentials
  • Retrieve private conversations or confidential documents
This type of security breach can have serious legal consequences, loss of customer trust, and significant financial damages for organizations.

Manipulation and Execution of Unauthorized Actions

Attackers leveraging Prompt Injection can force the model to perform actions outside the authorized scope:
  • Sending spam or phishing emails on behalf of the victim
  • Changing or deleting data in connected systems
  • Executing unauthorized financial transactions
  • Manipulating outputs to mislead users
  • Infiltrating related systems through APIs
These threats can be catastrophic, especially in critical applications such as banking systems, e-commerce platforms, or enterprise resource management systems.

Attacks on AI-Equipped Browsers

With the emergence of AI-powered browsers that have the capability to automate tasks and interact with the web, Prompt Injection has created a new threat. Researchers have shown that attackers can, through content embedded in websites:
  • Take control of the user's browser
  • Conduct financial transactions without user permission
  • Steal sensitive information such as passwords or credit card information
  • Create backdoors for subsequent access
This can expose users to serious financial and security risks.

Cross-Modal Vulnerabilities in Multimodal Models

Multimodal models capable of processing text, images, audio, and video introduce new vulnerabilities. Attackers can:
  • Hide malicious commands in images
  • Use inter-modal interactions to bypass security filters
  • Execute complex Cross-Modal attacks that are difficult to detect
This highlights the importance of developing specialized defenses for multimodal models.

Defense Methods Against Prompt Injection

Despite existing challenges, various strategies have been developed to reduce the risk of Prompt Injection attacks. Using a Defense-in-Depth approach is the best way to protect against these threats:

Instruction-Data Separation

One of the most fundamental and effective strategies is clear separation between system instructions and user input data:
  • Using Delimiters to distinguish between instructions and content
  • Implementing Structured Queries (StruQ) that structurally separate instructions from data
  • Using specific formats like JSON or XML to define instruction boundaries
  • Creating an Instruction Hierarchy that maintains system instruction priority
These methods help the model clearly identify which part of the input should be processed as an instruction and which part as data.

Input Filtering and Validation

Implementing robust filtering systems to identify and block suspicious inputs:
  • Using Regular Expressions to identify malicious patterns
  • Checking Perplexity Score to detect unnatural inputs
  • Applying Input Sanitization to remove or neutralize dangerous characters
  • Using Prompt Guards that examine inputs before reaching the main model
This defensive layer can neutralize many attack attempts before they reach the main model.

Fine-Tuning and Preference Optimization

Advanced machine learning techniques can increase model resistance to Prompt Injection:
  • SecAlign: A preference optimization method that trains the model to be more resistant to attacks
  • Adversarial Training: Training the model with attack samples for better identification of malicious attempts
  • Defensive Fine-Tuning: Fine-tuning the model with data containing attack patterns and appropriate responses
These methods improve security without increasing computational costs or requiring additional human resources.

Access Control and Sandboxing

Limiting model access and capabilities:
  • Applying the Principle of Least Privilege
  • Using API Rate Limiting to prevent automated attacks
  • Implementing Sandboxing to run the model in isolated environments
  • Monitoring and logging all interactions to identify suspicious behaviors
These measures can minimize potential damage from a successful attack.

Paraphrasing and Semantic Analysis

Advanced techniques that analyze input content before sending it to the main model:
  • Paraphrasing: Rewriting user input in simpler language that preserves the original meaning but removes hidden commands
  • Intent Detection: Identifying the user's true intent and detecting manipulation attempts
  • Semantic Analysis: Deep semantic analysis to identify inconsistencies between apparent content and actual intent
These methods are particularly effective against complex and multi-stage attacks.

AI-Based Monitoring and Detection

Using AI systems for real-time attack attempt detection:
  • Anomaly Detection: Identifying unusual behaviors in usage patterns
  • Behavioral Analysis: Analyzing user behavior to detect suspicious attempts
  • Multi-Model Verification: Using multiple models to verify outputs
  • Real-time Threat Intelligence: Using up-to-date information about new attack techniques
This dynamic approach can help organizations adapt to emerging and evolving threats.

Real-World Examples and Case Studies

Better understanding the Prompt Injection threat requires examining documented real-world cases:

Google Gemini Vulnerability

Security researchers recently discovered serious vulnerabilities in Google's Gemini model that enabled Prompt Injection and Search Injection. These flaws could lead to:
  • User privacy violations
  • Theft of data stored in Google Cloud
  • Unauthorized access to sensitive information
Google patched these vulnerabilities, but this case demonstrates the importance of security even in products from major tech companies.

Attack on Perplexity Comet

Brave researchers demonstrated how to attack the AI-centric Perplexity Comet browser through Indirect Prompt Injection. This vulnerability enabled:
  • Control of browser behavior
  • Execution of unauthorized actions
  • Access to user data
This case highlighted the importance of new security architectures for AI-powered browsers.

CVE-2024-5184 Attack

A documented vulnerability in LLM-based email assistants that allowed attackers to:
  • Inject commands through malicious emails
  • Access sensitive information
  • Manipulate other email content
This specific case showed how Indirect Prompt Injection can be exploited in real-world applications.

Future Challenges and the Path Forward

With the continuous advancement of language models and the expansion of their applications, new challenges will also emerge in the Prompt Injection security domain:

Agentic and Autonomous Models

AI models that can autonomously make decisions and perform complex actions increase the level of risk. These systems, examined in articles such as autonomous artificial intelligence and Agentic AI, require higher levels of security.

Integration with Critical Systems

With greater AI integration into critical infrastructure such as:
  • Financial and banking systems
  • Power and water networks
  • Smart transportation systems
  • Medical equipment
The potential consequences of Prompt Injection attacks can become more serious and widespread.

Emergence of Advanced Attack Techniques

Attackers constantly devise new methods to bypass defenses:
  • Using Steganography to hide commands in digital media
  • Multi-Step attacks that use multiple stages to bypass filters
  • Exploiting Model-Specific Weaknesses in each particular model
  • Using Social Engineering combined with Prompt Injection

Need for Global Security Standards

The industry has an increasing need for:
  • Development of common security standards
  • Creation of legal and regulatory frameworks
  • International cooperation to combat threats
  • Extensive training and awareness for developers and users
To effectively deal with this growing threat.

The Role of AI in Defense and Attack

Interestingly, AI itself can be used both for attack and defense against Prompt Injection. This creates a complex challenge where:

Offensive Use of AI

  • Attackers can use language models to automatically generate malicious Prompts
  • Tools like LLM can be used to find vulnerabilities
  • Machine learning techniques can be used to optimize attacks

Defensive Use of AI

  • Detection systems based on machine learning can identify attack patterns
  • Defensive models can analyze inputs before they reach the main model
  • Neural networks can be trained to identify complex anomalies

Connection to Other AI Domains

Prompt Injection has close connections to many other AI domains:

Prompt Engineering and Security

Prompt Engineering, the art of designing effective commands for language models, is directly related to Prompt Injection. A deep understanding of Prompt Engineering can help both developers design more secure systems and security analysts identify vulnerabilities.

Multimodal AI and Security Challenges

Multimodal models capable of processing various types of data have their own specific security challenges. Cross-Modal Prompt Injection attacks can use interactions between different modalities to bypass defenses.

RAG and New Vulnerabilities

RAG (Retrieval-Augmented Generation) systems that use external sources to improve responses are particularly vulnerable to Indirect Prompt Injection. Any external source can potentially contain malicious commands.

Agent-based Systems

Multi-agent systems and AI Agents that can autonomously perform complex actions can cause serious damage if exposed to Prompt Injection.

Impact on Different Industries

Prompt Injection has different impacts on various industries:

Financial Services

In the financial industry that uses AI in financial analysis and predictive financial modeling, Prompt Injection can lead to:
  • Manipulation of financial transactions
  • Leakage of confidential customer information
  • Incorrect investment decisions

Healthcare

AI systems in diagnosis and treatment, if exposed to these attacks, can:
  • Provide incorrect diagnoses
  • Disclose patient data
  • Issue incorrect treatment orders

Cybersecurity

The impact of AI on cybersecurity is bidirectional. While AI can help strengthen security, Prompt Injection can itself target security systems.

Education

With the impact of AI on the education industry, students and teachers must be aware of Prompt Injection dangers to prevent abuse of educational systems.

Best Practices for Secure Development

For developers and organizations wanting to build secure LLM-based applications:

In the Design Phase

  • Security by Design: Include security in the system architecture from the beginning
  • Threat Modeling: Identify and assess potential threats
  • Minimal Privileges: Grant only necessary access
  • Input Validation: Validate all inputs without exception

In the Implementation Phase

  • Use secure libraries and frameworks such as TensorFlow, PyTorch, and Keras
  • Implement multiple defensive layers
  • Use automated security testing tools
  • Complete documentation of system commands and limitations

In the Deployment Phase

  • Continuous Monitoring: Continuous monitoring of system behavior
  • Regular Updates: Regular updates of models and defensive systems
  • Incident Response Plan: Have an incident response plan
  • Security Audits: Conduct periodic security audits

Training and Awareness

  • Train the development team about Prompt Injection
  • Create a security culture in the organization
  • Continuously update knowledge about new threats
  • Share experiences and findings with the community

Tools and Resources for Protection

Several tools and resources exist to help developers protect against Prompt Injection:

Open Source Tools

  • LLM Guard: A security framework for protecting LLM applications
  • Prompt Injection Detector: Tools for automatic detection of Prompt Injection attempts
  • NeMo Guardrails: NVIDIA framework for creating security constraints

Cloud Services

  • Google Cloud AI and its security tools
  • Security services from major cloud providers
  • Specialized APIs for content filtering

Educational Resources

  • OWASP documentation on LLM security
  • Security researcher reports
  • Specialized training courses
  • Specialized AI security forums and groups

The Future of Prompt Injection and AI

Looking to the future, we can expect:

Development of More Resistant Models

Future generations of language models such as GPT-5, Claude 4, and future Gemini generations will likely have stronger built-in defensive mechanisms.

Security Standardization

The industry will move toward global standards for LLM security that include:
  • Common security protocols
  • Vulnerability assessment frameworks
  • Security certifications for AI applications

Integration with Other Technologies

Combination of AI with technologies such as:

The Role of Community and Collaboration

Fighting Prompt Injection requires widespread cooperation:

Developer Responsibility

Developers working with tools like ChatGPT, Claude, or DeepSeek must prioritize security.

Role of Researchers

Researchers must continue to:
  • Discover new vulnerabilities
  • Develop innovative defensive solutions
  • Share findings with the community

Organizational Responsibility

Companies using AI must:
  • Invest in security
  • Train employees
  • Have clear security policies

User Awareness

End users must also:
  • Be aware of the dangers
  • Adopt safe digital behaviors
  • Report suspicious cases

Conclusion

Prompt Injection is one of the most serious security threats in the era of generative AI, which has gained increasing importance with the expansion of large language model use in various applications and services. This threat can not only lead to sensitive information leakage, system manipulation, and execution of unauthorized actions, but with more complex AI systems and their integration with critical infrastructure, its consequences can become broader and more dangerous.
A deep understanding of attack mechanisms, different types of Prompt Injection, and defensive strategies is essential for all stakeholders in the AI ecosystem. From developers building LLM-based applications to end users interacting with these systems, everyone must play their role in creating a secure environment.
Fortunately, the cybersecurity and AI community is actively working on innovative solutions to combat this threat. From advanced techniques like SecAlign and Structured Queries to more secure architectures and automatic detection tools, significant progress is being made. However, this is an ongoing race between attackers and defenders that requires vigilance, continuous updates, and widespread collaboration.
Ultimately, success in combating Prompt Injection depends on a comprehensive and multi-layered approach that includes secure design, precise implementation, continuous monitoring, ongoing training, and collaboration across all industry sectors. By accepting this challenge and taking proactive measures, we can benefit from the amazing advantages of generative AI while maintaining security and privacy.
The future of AI is bright, but we can only fully benefit from its potential when we consider security as a fundamental priority and are prepared against threats like Prompt Injection.