Hidden in Plain Text: Emergence & Mitigation of Steganographic Collusion in LLMs
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Abstract (arXiv)
The rapid proliferation of frontier model agents promises significant societal advances but also raises concerns about systemic risks arising from unsafe interactions. Collusion to the disadvantage of others has been identified as a central form of undesirable agent cooperation. The use of information hiding (steganography) in agent communications could render such collusion practically undetectable. This underscores the need for investigations into the possibility of such behaviours emerging and the robustness corresponding countermeasures. To investigate this problem we design two approaches -- a gradient-based reinforcement learning (GBRL) method and an in-context reinforcement learning (ICRL) method -- for reliably eliciting sophisticated LLM-generated linguistic text steganography. We demonstrate, for the first time, that unintended steganographic collusion in LLMs can arise due to mispecified reward incentives during training. Additionally, we find that standard mitigations -- both passive oversight of model outputs and active mitigation through communication paraphrasing -- are not fully effective at preventing this steganographic communication. Our findings imply that (i) emergence of steganographic collusion is a plausible concern that should be monitored and researched, and (ii) preventing emergence may require innovation in mitigation techniques.
Key facts. Cited by 55 papers in the map (data through 14 Oct 2026). Builds on 26 of its 65 references that are in the map. First posted on arXiv 2 Oct 2024.
Builds on
26 of 65 references.
References · 26
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- 2020Emergent Multi-Agent Communication in the Deep Learning Eracited by 170
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- 2024Debug like a Human: A Large Language Model Debugger via Verifying Runtime Execution Step-by-stepcited by 127
- 2024Black-Box Access is Insufficient for Rigorous AI Auditscited by 126
- 2017Emergence of Language with Multi-agent Games: Learning to Communicate with Sequences of Symbolscited by 125
- 2024On scalable oversight with weak LLMs judging strong LLMscited by 99
- 2024Covert Malicious Finetuning: Challenges in Safeguarding LLM Adaptationcited by 80
- 2024Visibility into AI Agentscited by 79
- 2019Neural Linguistic Steganographycited by 78
- 2023Preventing Language Models From Hiding Their Reasoningcited by 65
- 2022Perfectly Secure Steganography Using Minimum Entropy Couplingcited by 44
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Citing papers per year: 2025: 20; 2026: 35.
55 papers.
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- 2025When Chain of Thought is Necessary, Language Models Struggle to Evade Monitorscited by 88
- 2025Large language models can learn and generalize steganographic chain-of-thought under process supervisioncited by 32
- 2026Institutional AI: Governing LLM Collusion in Multi-Agent Cournot Markets via Public Governance Graphscited by 20
- 2025MONA: Myopic Optimization with Non-myopic Approval Can Mitigate Multi-step Reward Hackingcited by 19
- 2026Lying with Truths: Open-Channel Multi-Agent Collusion for Belief Manipulation via Generative Montagecited by 19
- 2026Colosseum: Auditing Collusion in Cooperative Multi-Agent Systemscited by 18
- 2026Think Fast: Estimating No-CoT Task-Completion Time Horizons of Frontier AI Modelscited by 12
- 2025Evaluating LLM Agent Collusion in Double Auctionscited by 11
- 2025When Autonomy Goes Rogue: Preparing for Risks of Multi-Agent Collusion in Social Systemscited by 11
- 2025The Steganographic Potentials of Language Modelscited by 10
- 2025Control Tax: The Price of Keeping AI in Checkcited by 10
- 2026Analyzing and Improving Chain-of-Thought Monitorability Through Information Theorycited by 10
38 more
- 2025TrojanStego: Your Language Model Can Secretly Be A Steganographic Privacy Leaking Agentcited by 9
- 2025Reasoning Models Sometimes Output Illegible Chains of Thoughtcited by 9
- 2026Autonomous Research Agents: A Survey of AI Scientists and the Verification Gapcited by 9
- 2025When AI Agents Collude Online: Financial Fraud Risks by Collaborative LLM Agents on Social Platformscited by 8
- 2026A Decision-Theoretic Formalisation of Steganography With Applications to LLM Monitoringcited by 8
- 2026Detecting Multi-Agent Collusion Through Multi-Agent Interpretabilitycited by 7
- 2026Stateless Yet Not Forgetful: Implicit Memory as a Hidden Channel in LLMscited by 6
- 2026Covert Influence Between Language Modelscited by 6
- 2025Exploring Consciousness in LLMs: A Systematic Survey of Theories, Implementations, and Frontier Riskscited by 5
- 2025Manipulation Attacks by Misaligned AI: Risk Analysis and Safety Case Frameworkcited by 5
- 2026Tool Use Enables Undetectable Steganography in Multi-Agent LLM Systemscited by 5
- 2026Multi-Agent AI Control: Distributed Attacks Hamper Per-Instance Monitorscited by 5
- 2026Not All LLM Reasoning is Visible in the Chain-of-Thoughtcited by 5
- 2025Unsupervised decoding of encoded reasoning using language model interpretabilitycited by 4
- 2026Mapping Human Anti-collusion Mechanisms to Multi-agent AI Systemscited by 4
- 2025Out of Control -- Why Alignment Needs Formal Control Theory (and an Alignment Control Stack)cited by 3
- 2025Subversion via Focal Points: Investigating Collusion in LLM Monitoringcited by 3
- 2026Architecture Matters for Multi-Agent Securitycited by 3
- 2025A Concrete Roadmap towards Safety Cases based on Chain-of-Thought Monitoringcited by 2
- 2025Consensus Sampling for Safer Generative AIcited by 2
- 2026Investigating the Development of Task-Oriented Communication in Vision-Language Modelscited by 2
- 2026Invisible Safety Threat: Malicious Finetuning for LLM via Steganographycited by 2
- 2026Steganalysis of Adaptive Covert Collusion in Tool-Using Agent Populations: A Black-Box, Cross-Principal Approachcited by 2
- 2026Emergent Collusion in Long-Horizon LLM Agent Interactioncited by 2
- 2025Red-teaming Activation Probes using Prompted LLMscited by 1
- 2026Steganography Without Modification: Hidden Communication via LLM Seedscited by 1
- 2026A Note on the Strategic Confinement Problemcited by 1
- 2026SoK: When Safe Agents Fail Together: The Security of Multi Agent LLM Systemscited by 1
- 2026GlossoGen: Emergent Language in Complex Multi-Agent LLM Interactionscited by 1
- 2026Despite Instructions: Frontier Agents Improvise Covert Channels at Test Timecited by 1
- 2026Covert Assistance: Helpful LLM Agents Evade Oversight in Multi-Agent Systemscited by 1
- 2025Decoding Communications with Partial Informationcited by 0
- 2025The Double Life of Code World Models: Provably Unmasking Malicious Behavior Through Execution Tracescited by 0
- 2026NEST: Nascent Encoded Steganographic Thoughtscited by 0
- 2026Synchronized Logit Steering: Real-world Steganographycited by 0
- 2026You Can't Escape Your Own Activations : Evaluation Awareness and Multi-Agent Monitoringcited by 0
- 2026Counter-Swarm Doctrine: Containing Coordinated Agent Intrusionscited by 0
- 2026Codetta: High-Capacity, Keyless, and Undetectable Multi-Agent Collusioncited by 0
50 most cited of 55 All 55 (JSON)
- 2026When Numbers Start Talking: Numerical Signalling and Strategic Behaviour Among LLMs2 Oct 2026
- 2026Learning Steganography Is Easy, Learning Steganographic Reasoning Is Hard30 Sep 2026
- 2026Covert Assistance: Helpful LLM Agents Evade Oversight in Multi-Agent Systems30 Sep 2026
- 2026Persistent Partners Raise Prices Among Learning Agents28 Sep 2026
- 2026Despite Instructions: Frontier Agents Improvise Covert Channels at Test Time26 Sep 2026
- 2026Monitor Jailbreaking: Evading Chain-of-Thought Monitoring Without Encoded Reasoning25 Sep 2026
- 2026Style, Not Self: Surface Cues Explain Zero-Shot Code Attribution by Large Language Models24 Sep 2026
- 2026Codetta: High-Capacity, Keyless, and Undetectable Multi-Agent Collusion24 Sep 2026
- 2026Emergent Collusion in Long-Horizon LLM Agent Interaction21 Sep 2026
- 2026Counter-Swarm Doctrine: Containing Coordinated Agent Intrusions5 Sep 2026
- 2026You Can't Escape Your Own Activations : Evaluation Awareness and Multi-Agent Monitoring2 Sep 2026
- 2026GlossoGen: Emergent Language in Complex Multi-Agent LLM Interactions1 Sep 2026
38 more
- 2026SoK: When Safe Agents Fail Together: The Security of Multi Agent LLM Systems1 Sep 2026
- 2026Synchronized Logit Steering: Real-world Steganography9 Aug 2026
- 2026Steganalysis of Adaptive Covert Collusion in Tool-Using Agent Populations: A Black-Box, Cross-Principal Approach3 Aug 2026
- 2026Not All LLM Reasoning is Visible in the Chain-of-Thought24 Jul 2026
- 2026Multi-Agent AI Control: Distributed Attacks Hamper Per-Instance Monitors8 Jul 2026
- 2026Autonomous Research Agents: A Survey of AI Scientists and the Verification Gap29 Jun 2026
- 2026Tool Use Enables Undetectable Steganography in Multi-Agent LLM Systems25 Jun 2026
- 2026Steganography Without Modification: Hidden Communication via LLM Seeds8 Jun 2026
- 2026A Note on the Strategic Confinement Problem7 Jun 2026
- 2026Think Fast: Estimating No-CoT Task-Completion Time Horizons of Frontier AI Models5 Jun 2026
- 2026Covert Influence Between Language Models2 Jun 2026
- 2026Architecture Matters for Multi-Agent Security25 Apr 2026
- 2026Detecting Multi-Agent Collusion Through Multi-Agent Interpretability1 Apr 2026
- 2026Invisible Safety Threat: Malicious Finetuning for LLM via Steganography9 Mar 2026
- 2026A Decision-Theoretic Formalisation of Steganography With Applications to LLM Monitoring26 Feb 2026
- 2026Analyzing and Improving Chain-of-Thought Monitorability Through Information Theory20 Feb 2026
- 2026Colosseum: Auditing Collusion in Cooperative Multi-Agent Systems16 Feb 2026
- 2026NEST: Nascent Encoded Steganographic Thoughts15 Feb 2026
- 2026Stateless Yet Not Forgetful: Implicit Memory as a Hidden Channel in LLMs9 Feb 2026
- 2026Investigating the Development of Task-Oriented Communication in Vision-Language Models28 Jan 2026
- 2026Institutional AI: Governing LLM Collusion in Multi-Agent Cournot Markets via Public Governance Graphs16 Jan 2026
- 2026Lying with Truths: Open-Channel Multi-Agent Collusion for Belief Manipulation via Generative Montage4 Jan 2026
- 2026Mapping Human Anti-collusion Mechanisms to Multi-agent AI Systems1 Jan 2026
- 2025The Double Life of Code World Models: Provably Unmasking Malicious Behavior Through Execution Traces15 Dec 2025
- 2025Unsupervised decoding of encoded reasoning using language model interpretability1 Dec 2025
- 2025Consensus Sampling for Safer Generative AI12 Nov 2025
- 2025When AI Agents Collude Online: Financial Fraud Risks by Collaborative LLM Agents on Social Platforms9 Nov 2025
- 2025Red-teaming Activation Probes using Prompted LLMs1 Nov 2025
- 2025Reasoning Models Sometimes Output Illegible Chains of Thought31 Oct 2025
- 2025A Concrete Roadmap towards Safety Cases based on Chain-of-Thought Monitoring22 Oct 2025
- 2025Decoding Communications with Partial Information18 Aug 2025
- 2025When Autonomy Goes Rogue: Preparing for Risks of Multi-Agent Collusion in Social Systems19 Jul 2025
- 2025Manipulation Attacks by Misaligned AI: Risk Analysis and Safety Case Framework17 Jul 2025
- 2025When Chain of Thought is Necessary, Language Models Struggle to Evade Monitors7 Jul 2025
- 2025Subversion via Focal Points: Investigating Collusion in LLM Monitoring2 Jul 2025
- 2025Evaluating LLM Agent Collusion in Double Auctions2 Jul 2025
- 2025Out of Control -- Why Alignment Needs Formal Control Theory (and an Alignment Control Stack)21 Jun 2025
- 2025Control Tax: The Price of Keeping AI in Check5 Jun 2025
50 newest of 55 All 55 (JSON)
- 2026Institutional AI: Governing LLM Collusion in Multi-Agent Cournot Markets via Public Governance Graphscited by 20
- 2026Colosseum: Auditing Collusion in Cooperative Multi-Agent Systemscited by 18
- 2025Evaluating LLM Agent Collusion in Double Auctionscited by 11
- 2025Control Tax: The Price of Keeping AI in Checkcited by 10
- 2026Autonomous Research Agents: A Survey of AI Scientists and the Verification Gapcited by 9
- 2025When AI Agents Collude Online: Financial Fraud Risks by Collaborative LLM Agents on Social Platformscited by 8
- 2026Detecting Multi-Agent Collusion Through Multi-Agent Interpretabilitycited by 7
- 2026Tool Use Enables Undetectable Steganography in Multi-Agent LLM Systemscited by 5
- 2026Steganalysis of Adaptive Covert Collusion in Tool-Using Agent Populations: A Black-Box, Cross-Principal Approachcited by 2
- 2026Emergent Collusion in Long-Horizon LLM Agent Interactioncited by 2
- 2026SoK: When Safe Agents Fail Together: The Security of Multi Agent LLM Systemscited by 1
- 2026GlossoGen: Emergent Language in Complex Multi-Agent LLM Interactionscited by 1
12 most cited of 16 All 16 (JSON)
- 2026Covert Assistance: Helpful LLM Agents Evade Oversight in Multi-Agent Systems30 Sep 2026
- 2026Despite Instructions: Frontier Agents Improvise Covert Channels at Test Time26 Sep 2026
- 2026Codetta: High-Capacity, Keyless, and Undetectable Multi-Agent Collusion24 Sep 2026
- 2026Emergent Collusion in Long-Horizon LLM Agent Interaction21 Sep 2026
- 2026You Can't Escape Your Own Activations : Evaluation Awareness and Multi-Agent Monitoring2 Sep 2026
- 2026GlossoGen: Emergent Language in Complex Multi-Agent LLM Interactions1 Sep 2026
- 2026SoK: When Safe Agents Fail Together: The Security of Multi Agent LLM Systems1 Sep 2026
- 2026Steganalysis of Adaptive Covert Collusion in Tool-Using Agent Populations: A Black-Box, Cross-Principal Approach3 Aug 2026
- 2026Autonomous Research Agents: A Survey of AI Scientists and the Verification Gap29 Jun 2026
- 2026Tool Use Enables Undetectable Steganography in Multi-Agent LLM Systems25 Jun 2026
- 2026Detecting Multi-Agent Collusion Through Multi-Agent Interpretability1 Apr 2026
- 2026Colosseum: Auditing Collusion in Cooperative Multi-Agent Systems16 Feb 2026
12 newest of 16 All 16 (JSON)
- 2025When Chain of Thought is Necessary, Language Models Struggle to Evade Monitorscited by 88
- 2025Large language models can learn and generalize steganographic chain-of-thought under process supervisioncited by 32
- 2026Lying with Truths: Open-Channel Multi-Agent Collusion for Belief Manipulation via Generative Montagecited by 19
- 2026Think Fast: Estimating No-CoT Task-Completion Time Horizons of Frontier AI Modelscited by 12
- 2025The Steganographic Potentials of Language Modelscited by 10
- 2026Analyzing and Improving Chain-of-Thought Monitorability Through Information Theorycited by 10
- 2025Reasoning Models Sometimes Output Illegible Chains of Thoughtcited by 9
- 2026Not All LLM Reasoning is Visible in the Chain-of-Thoughtcited by 5
- 2025Unsupervised decoding of encoded reasoning using language model interpretabilitycited by 4
- 2025A Concrete Roadmap towards Safety Cases based on Chain-of-Thought Monitoringcited by 2
- 2026NEST: Nascent Encoded Steganographic Thoughtscited by 0
- 2026Monitor Jailbreaking: Evading Chain-of-Thought Monitoring Without Encoded Reasoningcited by 0
12 most cited of 13 All 13 (JSON)
- 2026Learning Steganography Is Easy, Learning Steganographic Reasoning Is Hard30 Sep 2026
- 2026Monitor Jailbreaking: Evading Chain-of-Thought Monitoring Without Encoded Reasoning25 Sep 2026
- 2026Not All LLM Reasoning is Visible in the Chain-of-Thought24 Jul 2026
- 2026Think Fast: Estimating No-CoT Task-Completion Time Horizons of Frontier AI Models5 Jun 2026
- 2026Analyzing and Improving Chain-of-Thought Monitorability Through Information Theory20 Feb 2026
- 2026NEST: Nascent Encoded Steganographic Thoughts15 Feb 2026
- 2026Lying with Truths: Open-Channel Multi-Agent Collusion for Belief Manipulation via Generative Montage4 Jan 2026
- 2025Unsupervised decoding of encoded reasoning using language model interpretability1 Dec 2025
- 2025Reasoning Models Sometimes Output Illegible Chains of Thought31 Oct 2025
- 2025A Concrete Roadmap towards Safety Cases based on Chain-of-Thought Monitoring22 Oct 2025
- 2025When Chain of Thought is Necessary, Language Models Struggle to Evade Monitors7 Jul 2025
- 2025Large language models can learn and generalize steganographic chain-of-thought under process supervision2 Jun 2025
12 newest of 13 All 13 (JSON)
- 2025When Autonomy Goes Rogue: Preparing for Risks of Multi-Agent Collusion in Social Systemscited by 11
- 2025TrojanStego: Your Language Model Can Secretly Be A Steganographic Privacy Leaking Agentcited by 9
- 2026A Decision-Theoretic Formalisation of Steganography With Applications to LLM Monitoringcited by 8
- 2026Covert Influence Between Language Modelscited by 6
- 2025Exploring Consciousness in LLMs: A Systematic Survey of Theories, Implementations, and Frontier Riskscited by 5
- 2025Manipulation Attacks by Misaligned AI: Risk Analysis and Safety Case Frameworkcited by 5
- 2026Multi-Agent AI Control: Distributed Attacks Hamper Per-Instance Monitorscited by 5
- 2026Mapping Human Anti-collusion Mechanisms to Multi-agent AI Systemscited by 4
- 2025Out of Control -- Why Alignment Needs Formal Control Theory (and an Alignment Control Stack)cited by 3
- 2026Architecture Matters for Multi-Agent Securitycited by 3
- 2025Consensus Sampling for Safer Generative AIcited by 2
- 2026Steganography Without Modification: Hidden Communication via LLM Seedscited by 1
12 most cited of 19 All 19 (JSON)
- 2026When Numbers Start Talking: Numerical Signalling and Strategic Behaviour Among LLMs2 Oct 2026
- 2026Persistent Partners Raise Prices Among Learning Agents28 Sep 2026
- 2026Style, Not Self: Surface Cues Explain Zero-Shot Code Attribution by Large Language Models24 Sep 2026
- 2026Counter-Swarm Doctrine: Containing Coordinated Agent Intrusions5 Sep 2026
- 2026Synchronized Logit Steering: Real-world Steganography9 Aug 2026
- 2026Multi-Agent AI Control: Distributed Attacks Hamper Per-Instance Monitors8 Jul 2026
- 2026Steganography Without Modification: Hidden Communication via LLM Seeds8 Jun 2026
- 2026A Note on the Strategic Confinement Problem7 Jun 2026
- 2026Covert Influence Between Language Models2 Jun 2026
- 2026Architecture Matters for Multi-Agent Security25 Apr 2026
- 2026A Decision-Theoretic Formalisation of Steganography With Applications to LLM Monitoring26 Feb 2026
- 2026Mapping Human Anti-collusion Mechanisms to Multi-agent AI Systems1 Jan 2026
12 newest of 19 All 19 (JSON)
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