Padmaksha Roy

Machine learning researcher · Virginia Tech

Padmaksha Roy

I develop machine learning methods for recognizing anomalies that differ from those seen during training. My research connects anomaly detection, out-of-distribution generalization, and adversarial robustness, with applications in cybersecurity, multivariate time series, and cyber-physical systems.

At Virginia Tech, I study how useful structure in data—relationships between variables, shared information across domains, and the geometry of learned representations—can help models recognize unfamiliar behavior. I am also interested in large language models and in-context learning for zero-day anomaly detection.

Padmaksha Roy

ANOMALY Detection · Generalization · Robustness

Research

Google Scholar

Learning across tasksNormal-data learning and confidence calibration repeat across tasks; a separate diamond represents an unseen anomaly category.
Learning across tasks

2026International Conference on Data Mining · Machine Learning for Cybersecurity Workshop

A Multi-directional Meta-Learning Framework for Class-Generalizable Anomaly Detection

Padmaksha Roy, Lamine Mili, Almuatazbellah Boker

A detector must transfer what it learns from familiar data to recognize new anomaly categories. This framework first learns normal behavior, then uses a few examples of known anomalies to calibrate confidence. Repeating the process across training tasks helps distinguish normal observations from previously unseen attacks or abnormal heartbeats.

Joint structure, beyond marginalsTemporal traces feed a joint-dependence representation; the off-contour diamond marks a change in relationships between variables.
Joint structure, beyond marginals

2025Transactions on Machine Learning Research

Beyond Marginals: Learning Joint Spatio-Temporal Patterns for Multivariate Anomaly Detection

Padmaksha Roy, Almuatazbellah Boker, Lamine Mili

A system can behave abnormally even when each sensor looks plausible on its own. This work combines a transformer for temporal context with explicit models of how latent variables depend on one another. Contrastive training separates normal windows from anomalous ones, using a small labeled anomaly pool to create realistic perturbations.

Shared structure across domainsDifferent source-domain clusters pass through a compact bottleneck into a shared representation, reducing domain-specific variation.
Shared structure across domains

2025ECML-PKDD 2025 · Research Track

Improving Novel Anomaly Detection with Domain-Invariant Latent Representations

Padmaksha Roy, Ming Jin, Himanshu Singhal, Tyler Cody, Kevin Choi

Training on known attacks can teach a detector patterns that fail to transfer. This work combines classification and reconstruction with an information penalty on a compact latent representation. The aim is to retain useful detection evidence while reducing domain-specific correlations, improving generalization to anomaly categories held out during training.

Separating clean and poisoned dataPrediction residuals help partition candidate clean and poisoned subsets in a two-level robust regression problem.
Separating clean and poisoned data

2025IEEE Internet of Things Journal

Model Residuals as Shields: A Two-Level Formulation to Defend Smart Grids From Poisoning Attacks

Tung-Wei Lin, Padmaksha Roy, Yi Zeng, Ming Jin, Ruoxi Jia, Chen-Ching Liu, Alberto Sangiovanni-Vincentelli

Poisoned training data can undermine regression models used in smart-grid monitoring. This paper uses discrepancies between predictions and observations to separate candidate clean and corrupted subsets through a two-level optimization. It examines varied attack strategies and contamination levels, including majority-poisoned settings, while discussing the effects of temporal autocorrelation.

Learning under two kinds of attackCorrupted training samples and disguised deployment inputs are considered together through two coupled levels of defense.
Learning under two kinds of attack

2025AAAI-25 Workshop · AI for Cyber Security

Defense against Joint Poisoning and Evasion Attacks: A Case Study of DERMS

Zain ul Abdeen, Ahmad Al-Tawaha, Padmaksha Roy, Ruoxi Jia, Laura Freeman, Peter Beling, Chen-Ching Liu, Alberto Sangiovanni-Vincentelli, Ming Jin

Distributed-energy controllers can be attacked both by corrupting their training data and by disguising malicious commands at deployment. This work couples robust regression with detection-threshold selection in a bilevel learning problem, using local measurements to check expected commands. Experiments examine combined attacks on an IEEE 13-bus feeder.

The first three authors contributed equally.

Distance that respects correlationA tilted correlation ellipse distinguishes distance along a learned distribution from a nearby point outside that distribution.
Distance that respects correlation

2024PAKDD 2024

Latent Space Correlation-Aware Autoencoder for Anomaly Detection in Skewed Data

Padmaksha Roy, Himanshu Singhal, Timothy J. O’Shea, Ming Jin

An autoencoder for skewed sensor data combines reconstruction error with a robust Mahalanobis measure in latent space. Using median- and MAD-based statistics helps account for correlations that Euclidean reconstruction error misses, with the goal of separating anomalies close to normal observations as well as more distant anomalies.

Bridging security and learningAn open book bridges established data-security controls, shown by a lock, with distributed machine-learning systems.
Bridging security and learning

2023Survey · arXiv preprint

A Survey of Data Security: Practices from Cybersecurity and Challenges of Machine Learning

Padmaksha Roy, Jaganmohan Chandrasekaran, Erin Lanus, Laura Freeman, Jeremy Werner

Machine-learning systems introduce data-security risks across collection, storage, transmission, and computation. This survey connects established cybersecurity practices with privacy-preserving machine learning, reviewing access controls, cryptography, zero trust, differential privacy, and federated learning. It explains assumptions and trade-offs to help practitioners select protections for a system’s data lifecycle.

Mobility to probabilistic forecastsDirected mobility between county nodes informs a forecast with multiple plausible outcomes, represented by mixture-density curves.
Mobility to probabilistic forecasts

2021IEEE/ACM ASONAM 2021

Deep diffusion-based forecasting of COVID-19 by incorporating network-level mobility information

Padmaksha Roy, Shailik Sarkar, Subhodip Biswas, Fanglan Chen, Zhiqian Chen, Naren Ramakrishnan, Chang-Tien Lu

ARM3Dnet forecasts county-level COVID-19 outcomes by combining mobility-informed graph diffusion with autoregressive sequence modeling. A mixture-density output represents multiple plausible outcomes rather than a single deterministic forecast. The study evaluates how changing mobility relationships and probabilistic modeling affect forecasting accuracy and uncertainty on county-level epidemic data.

Training & experience

Background

Education

Aug 2021–Sept 2026

Ph.D., Computer Engineering

Virginia Tech

2019–2021

M.Eng., Computer Engineering

Virginia Tech

Focus in machine learning

Experience

2020–2021

Graduate Teaching Assistant

Virginia Tech

Machine Learning and Advanced Machine Learning

2017–2018

Senior Software Developer, Machine Learning

Accenture AI

Statistical learning, production recommendation systems, and interpretable models

2015–2016

Software Developer

Accenture Digital

Data analytics, cloud microservices, and deployment automation

Let’s talk research.

Open to conversations about machine learning opportunities.

padmaksha@vt.edu