Towards Causal Model-Based Policy Optimization

Real-world decision-making problems are often marked by complex, uncertain dynamics that can shift or break under changing conditions. Traditional Model-Based Reinforcement Learning (MBRL) approaches learn predictive models of environment dynamics from queried trajectories and then use these models to simulate rollouts for policy optimization. However, such methods do not account for the underlying causal mechanisms that govern the environment, and thus inadvertently capture spurious correlations, making them sensitive to distributional shifts and limiting their ability to generalize. The same naturally holds for model-free approaches. In this work, we introduce Causal Model-Based Policy Optimization (C-MBPO), a novel framework that integrates causal learning into the MBRL pipeline to achieve more robust, explainable, and generalizable policy learning algorithms. Our approach centers on first inferring a Causal Markov Decision Process (C-MDP) by learning a local Structural Causal Model (SCM) of both the state and reward transition dynamics from trajectories gathered online. C-MDPs differ from classic MDPs in that we can decompose causal dependencies in the environment dynamics via specifying an associated Causal Bayesian Network. C-MDPs allow for targeted interventions and counterfactual reasoning, enabling the agent to distinguish between mere statistical correlations and causal relationships. The learned SCM is then used to simulate counterfactual on-policy transitions and rewards under hypothetical actions (or ``interventions"), thereby guiding policy optimization more effectively. The resulting policy learned by C-MBPO can be shown to be robust to a class of distributional shifts that affect spurious, non-causal relationships in the dynamics. We demonstrate this through some simple experiments involving near and far OOD dynamics drifts.

Guidelines for Applying RL and MARL in Cybersecurity Applications

Reinforcement Learning (RL) and Multi-Agent Reinforcement Learning (MARL) have emerged as promising methodologies for addressing challenges in automated cyber defence (ACD). These techniques offer adaptive decision-making capabilities in high-dimensional, adversarial environments. This report provides a structured set of guidelines for cybersecurity professionals and researchers to assess the suitability of RL and MARL for specific use cases, considering factors such as explainability, exploration needs, and the complexity of multi-agent coordination. It also discusses key algorithmic approaches, implementation challenges, and real-world constraints, such as data scarcity and adversarial interference. The report further outlines open research questions, including policy optimality, agent cooperation levels, and the integration of MARL systems into operational cybersecurity frameworks. By bridging theoretical advancements and practical deployment, these guidelines aim to enhance the effectiveness of AI-driven cyber defence strategies.

Less is more? Rewards in RL for Cyber Defence

The last few years has seen an explosion of interest in autonomous cyber defence agents based on deep reinforcement learning. Such agents are typically trained in a cyber gym environment, also known as a cyber simulator, at least 32 of which have already been built. Most, if not all cyber gyms provide dense "scaffolded" reward functions which combine many penalties or incentives for a range of (un)desirable states and costly actions. Whilst dense rewards help alleviate the challenge of exploring complex environments, yielding seemingly effective strategies from relatively few environment steps; they are also known to bias the solutions an agent can find, potentially towards suboptimal solutions. Sparse rewards could offer preferable or more effective solutions and have been overlooked by cyber gyms to date. In this work we set out to evaluate whether sparse reward functions might enable training more effective cyber defence agents. Towards this goal we first break down several evaluation limitations in existing work by proposing a ground truth evaluation score that goes beyond the standard RL paradigm used to train and evaluate agents. By adapting a well-established cyber gym to accommodate our methodology and ground truth score, we propose and evaluate two sparse reward mechanisms and compare them with a typical dense reward. Our evaluation considers a range of network sizes, from 2 to 50 nodes, and both reactive and proactive defensive actions. Our results show that sparse rewards, particularly positive reinforcement for an uncompromised network state, enable the training of more effective cyber defence agents. Furthermore, we show that sparse rewards provide more stable training than dense rewards, and that both effectiveness and training stability are robust to a variety of cyber environment considerations.

International AI Safety Report

The first International AI Safety Report comprehensively synthesizes the current evidence on the capabilities, risks, and safety of advanced AI systems. The report was mandated by the nations attending the AI Safety Summit in Bletchley, UK. Thirty nations, the UN, the OECD, and the EU each nominated a representative to the report's Expert Advisory Panel. A total of 100 AI experts contributed, representing diverse perspectives and disciplines. Led by the report's Chair, these independent experts collectively had full discretion over the report's content.

Humanity's Last Exam

Benchmarks are important tools for tracking the rapid advancements in large language model (LLM) capabilities. However, benchmarks are not keeping pace in difficulty: LLMs now achieve over 90\% accuracy on popular benchmarks like MMLU, limiting informed measurement of state-of-the-art LLM capabilities. In response, we introduce Humanity's Last Exam (HLE), a multi-modal benchmark at the frontier of human knowledge, designed to be the final closed-ended academic benchmark of its kind with broad subject coverage. HLE consists of 3,000 questions across dozens of subjects, including mathematics, humanities, and the natural sciences. HLE is developed globally by subject-matter experts and consists of multiple-choice and short-answer questions suitable for automated grading. Each question has a known solution that is unambiguous and easily verifiable, but cannot be quickly answered via internet retrieval. State-of-the-art LLMs demonstrate low accuracy and calibration on HLE, highlighting a significant gap between current LLM capabilities and the expert human frontier on closed-ended academic questions. To inform research and policymaking upon a clear understanding of model capabilities, we publicly release HLE at https://lastexam.ai.

An Attentive Graph Agent for Topology-Adaptive Cyber Defence

As cyber threats grow increasingly sophisticated, reinforcement learning is emerging as a promising technique to create intelligent, self-improving defensive systems. However, most existing autonomous defensive agents have overlooked the inherent graph structure of computer networks subject to cyber attacks, potentially missing critical information. To address this gap, we developed a custom version of the Cyber Operations Research Gym (CybORG) environment that encodes the observable network state as a directed graph, utilizing realistic and interpretable low-level features. %, like number of open ports and unexpected detected connections. We leverage a Graph Attention Network (GAT) architecture to process node, edge, and global features, and modify its output to be compatible with policy gradient methods in reinforcement learning. GAT policies offer several advantages over standard approaches based on simplistic flattened state observations. They can handle the changes in network topology that occur at runtime when dynamic connections between hosts appear. Policies can be deployed to networks that differ in size to the ones seen during training, enabling a degree of generalisation inaccessible with alternative approaches. Furthermore, the graph neural network policies outputs are explainable in terms of tangible network properties, providing enhanced interpretability of defensive actions. We verify that our low-level graph observations are meaningful enough to train GAT defensive policies that are able to adapt to changing topologies. We evaluate how our trained policies perform when deployed on networks of varying sizes with the same subnetwork structure, comparing them against policies specifically trained for each network configuration. Our study contributes to the development of robust cyber defence systems that can better adapt to real-world network security challenges.

SoK: On Closing the Applicability Gap in Automated Vulnerability Detection

The frequent discovery of security vulnerabilities in both open-source and proprietary software underscores the urgent need for earlier detection during the development lifecycle. Initiatives such as DARPA's Artificial Intelligence Cyber Challenge (AIxCC) aim to accelerate Automated Vulnerability Detection (AVD), seeking to address this challenge by autonomously analyzing source code to identify vulnerabilities. This paper addresses two primary research questions: (RQ1) How is current AVD research distributed across its core components? (RQ2) What key areas should future research target to bridge the gap in the practical applicability of AVD throughout software development? To answer these questions, we conduct a systematization over 79 AVD articles and 17 empirical studies, analyzing them across five core components: task formulation and granularity, input programming languages and representations, detection approaches and key solutions, evaluation metrics and datasets, and reported performance. Our systematization reveals that the narrow focus of AVD research-mainly on specific tasks and programming languages-limits its practical impact and overlooks broader areas crucial for effective, real-world vulnerability detection. We identify significant challenges, including the need for diversified problem formulations, varied detection granularities, broader language support, better dataset quality, enhanced reproducibility, and increased practical impact. Based on these findings we identify research directions that will enhance the effectiveness and applicability of AVD solutions in software security.

Inherently Interpretable and Uncertainty-Aware Models for Online Learning in Cyber-Security Problems

In this paper, we address the critical need for interpretable and uncertainty-aware machine learning models in the context of online learning for high-risk industries, particularly cyber-security. While deep learning and other complex models have demonstrated impressive predictive capabilities, their opacity and lack of uncertainty quantification present significant questions about their trustworthiness. We propose a novel pipeline for online supervised learning problems in cyber-security, that harnesses the inherent interpretability and uncertainty awareness of Additive Gaussian Processes (AGPs) models. Our approach aims to balance predictive performance with transparency while improving the scalability of AGPs, which represents their main drawback, potentially enabling security analysts to better validate threat detection, troubleshoot and reduce false positives, and generally make trustworthy, informed decisions. This work contributes to the growing field of interpretable AI by proposing a class of models that can be significantly beneficial for high-stake decision problems such as the ones typical of the cyber-security domain. The source code is available.

Fair Exploration and Exploitation

In this paper we consider the contextual bandit problem with a finite (or infinite and clustered) context set. We consider the fully adversarial problem in which, apart from having bounded losses, there are no assumptions whatsoever on the generation of the contexts and losses. In our problem we assume that the context set is partitioned into a set of protected groups. At the start of each trial we are given a probability distribution over the context set and are required (on that trial) to be fair with respect to that distribution, in that if the context (for that trial) was drawn from the distribution then our choice of action would be unbiased towards any protected group. We develop an algorithm FexEx for this problem which has remarkable efficiency, having a space and per-trial time complexity at most linear in the dimensionality of the policy space. FexEx can handle non-stationarity, in that its regret can be bounded with respect to any sequence of policies satisfying the fairness constraints. For such a sequence the regret bound of FexEx is essentially the same as that of running Exp3.S for each context independently (an approach that does not satisfy the fairness constraints).

Benchmarking OpenAI o1 in Cyber Security

We evaluate OpenAI's o1-preview and o1-mini models, benchmarking their performance against the earlier GPT-4o model. Our evaluation focuses on their ability to detect vulnerabilities in real-world software by generating structured inputs that trigger known sanitizers. Using DARPA's AI Cyber Challenge (AIxCC) framework and the Nginx challenge project--a deliberately modified version of the widely-used Nginx web server--we create a well-defined yet complex environment for testing LLMs on automated vulnerability detection (AVD) tasks. Our results show that the o1-preview model significantly outperforms GPT-4o in both success rate and efficiency, especially in more complex scenarios.