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Code for the paper "PyMalEvasion: Generative AI-based Adversarial Evasion in Python Scripts"

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CrowdStrike/pymalevasion

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PyMalEvasion: Generative AI-based Adversarial Evasion in Python Scripts

Data is available at DOI

Dataset

Name Type Clean Dirty Total
Ours (train) Script 15,242 11,456 26,698
Ours (valid) Script 1,075 2,046 3,121
Ours (test) Script 603 1,760 2,363
Ours (all) Script 16,920 15,262 32,182
Ours (adv_test) Script 0 5,332 5,332

The PyMalEvasion dataset is constructed by augmenting the PyPI Malregistry dataset with samples from VT. You can use this script to extract the sources from the archived PyPI Malregistry. After extracting the sources, we filtered out those under 512 bytes (e.g. containing typically harmless initialization or configuration scripts).

We further split the data into train/valid/test following a cluster-informed method. We apply the shallow FX, UMAP for dimensionality reduction and HDBSCAN for the actual clustering. Finally, the splits are chosen such that all samples in a cluster are from a single split, thus minimizing potential information leakage.

Adversarial generation

  • Heuristics (simple modifications to add comments, documentation, padding)
  • LLM constrained via AST and RAG
  • LLM unconstrained

For AST-based constrained generation, the LLM is instructed to generate an action (add/edit/delete) and a code snippet for which the action to take place. Then, the AST of the original script is updated from the (smaller) AST of the snippet.

Classifiers

We employ 3 classification strategies: shallow (XGBoost on handcrafted features), CodeBERT (adapted from microsoft/CodeBERT, base model: microsoft/codebert-base) and LLM-based.

For the shallow classification we built 8 feature types and trained an XGBoost model for each one of the 255 feature combinations. Models are trained with HPO and 5-fold cross-validation.

Support statement

PyMalEvasion is an open source project, not a CrowdStrike product. As such, it carries no formal support, expressed or implied.

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Code for the paper "PyMalEvasion: Generative AI-based Adversarial Evasion in Python Scripts"

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