---
license: mit
library_name: pytorch
tags:
  - cti
  - attack-classification
  - mitre-attack
  - cybersecurity
  - text-classification
  - multi-label-classification
language:
  - en
base_model: ibm-research/CTI-BERT
---

# CASSANDRA — BCE configuration on TRAM2

Fine-tuned CTI-BERT models for extracting MITRE ATT&CK techniques from cyber threat intelligence (CTI) reports. This repository contains the **BCE configuration** of the CASSANDRA recipe trained on **TRAM2** (50 ATT&CK sub-techniques), comprising **3 ensemble members** trained with seeds {42, 123, 456}.

> Anonymous artifact for ACM CCS 2026 review. Final author identification will be added after review.

## Headline result

On the **TRAM2** test set (30 scored documents):

- **3-seed ensemble per-document F1 (τ=0.5): 73.87%**
- Exceeds Llama 3.1 8B (72.50%, Buchel et al. 2025) at 73× fewer parameters.

The per-seed table below shows the live artifact's individual seed F1s and ensemble F1; small variance from the headline (≤0.3 F1) reflects inference-time floating-point ordering on different hardware. Full per-seed and ensemble metrics are in [`results.json`](./results.json).

## Architecture

`LabelAttentionClassifier`: a 110M-parameter CTI-BERT encoder followed by a per-label attention head.

- Encoder: [`ibm-research/CTI-BERT`](https://huggingface.co/ibm-research/CTI-BERT) (110M params, 768 hidden)
- Head: 50 learned 768-dim label queries that attend over the encoder's `last_hidden_state`, followed by a shared 1-output linear layer applied per-label
- Loss: BCE with `pos_weight=5.0`
- Regularization / training tricks: layer-wise learning rate decay (α=0.85), exponential moving average (β=0.999), multi-seed probability averaging at inference

The architecture is custom (not derived from `transformers.PreTrainedModel`), so loading requires the [`modeling.py`](./modeling.py) file shipped with this repo.

## Training data

- **TRAM2** (Threat Report ATT&CK Mapping v2): 151 reports, 19,178 sentences, 50 ATT&CK sub-techniques. Mean of ~82 positive examples per class.
- **Splits**: report-level train/test split from Buchel et al. (2025) "SoK: A Survey of Approaches for ATT&CK Classifier Construction" (120 train reports, 31 test reports — one test report excluded from per-document F1 due to empty in-vocabulary ground truth).
- **Validation**: 80:20 sentence-level random split within the training reports for early stopping and threshold selection.

## Intended use

Map free-text CTI sentences (analyst reports, incident write-ups, vendor advisories) to ATT&CK techniques. The model takes a single sentence and outputs a probability for each of 50 techniques.

**Aggregation to document level (paper convention):** apply per-sentence inference, take the per-class max across sentences in a document, threshold that, report the union of predicted techniques per document. F1 is computed against the document-level technique set.

**Limitations:**
- Trained on English-language CTI; behavior on other languages is not characterized.
- The label vocabulary is fixed at the 50 TRAM2 sub-techniques.
- Within TRAM2, the rarest techniques have ~7 positive examples; predictions for these classes are noisier than for densely-populated techniques.

## How to load and run

```python
from modeling import load_ensemble, predict_ensemble
import os, glob

seed_dirs = sorted(glob.glob(os.path.join(os.path.dirname(__file__), "seeds", "seed-*")))
seeds = load_ensemble(seed_dirs, device="cuda")

sentences = [
    "The malware uses Windows Command Shell to execute encoded scripts.",
    "After initial access, persistence was established via Registry Run Keys.",
]
results = predict_ensemble(seeds, sentences, threshold=0.5)
for sentence, techniques in results:
    print(sentence, "->", techniques)
```

A complete CLI example is in [`inference_example.py`](./inference_example.py):

```bash
pip install -r requirements.txt
python inference_example.py
```

## Per-seed members

| Seed | Per-document F1 (τ=0.5) | Selected weights |
|---|---|---|
| 42  | 73.78% | EMA |
| 123 | 71.97% | EMA |
| 456 | 75.59% | EMA |
| **3-seed ensemble** | **73.87%** | — |

For verification without re-running the model, each seed directory contains a `seed_probs.npz` file with the model's per-sentence sigmoid probabilities on the test and dev splits — sufficient to recompute every F1 number in the model card.

## Citation

```bibtex
@inproceedings{cassandra2026,
  title  = {CASSANDRA: How Many Parameters Suffice to Automate TTP Extractions from CTI Reports---Pushing Towards the Lower Bound},
  author = {Anonymous},
  booktitle = {Proceedings of the 2026 ACM SIGSAC Conference on Computer and Communications Security (CCS)},
  year   = {2026},
  note   = {Under review — anonymous submission}
}
```

Please also cite the TRAM2 dataset and the CTI-BERT encoder.

## License

MIT — see [`LICENSE`](./LICENSE).