---
license: apache-2.0
library_name: pytorch
tags:
  - cti
  - attack-classification
  - mitre-attack
  - cybersecurity
  - text-classification
  - multi-label-classification
  - asymmetric-loss
language:
  - en
base_model: ibm-research/CTI-BERT
---

# CASSANDRA — ASL configuration on TRAM2

Fine-tuned CTI-BERT models for extracting MITRE ATT&CK techniques from cyber threat intelligence (CTI) reports. This repository contains the **ASL configuration** of the CASSANDRA recipe trained on **TRAM2** (50 ATT&CK sub-techniques), comprising **6 ensemble members** trained with seeds {42, 123, 456, 789, 2024, 3141}.

This is the highest-F1 configuration in the CASSANDRA paper on TRAM2. The asymmetric loss + 6-seed ensemble adds +3.30 F1 over the BCE 3-seed configuration ([`cassandra-bce-tram2`](https://huggingface.co/cassandra-anon/cassandra-bce-tram2)).

> Anonymous artifact for double-blind peer review. Author information will be added after the review period.

## Headline result

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

- **6-seed ensemble per-document F1 at dev-tuned τ=0.59: 77.17%**
- 6-seed ensemble per-document F1 at uniform τ=0.5: 76.87%
- Bootstrap 95% CI (2000 resamples over the 30 test documents): **[70.72%, 82.42%]**

Comparison numbers from Buchel et al. (2025) on the same protocol:
- Llama 3.1 8B (generative): 72.50% — this configuration: 77.17% (+4.67 F1, 73× smaller)
- CySecBERT 110M: 69.74%
- CTI-BERT 110M (SoK baseline): 69.07%

The per-seed table below shows the live artifact's individual seed F1s and ensemble F1; small variance from the headline (≤0.5 F1) reflects inference-time floating-point ordering on different hardware. Full per-seed and ensemble metrics are in [`results.json`](./results.json).

## Architecture

`LabelAttentionClassifier` with asymmetric loss training:

- 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: **Asymmetric Loss** (Ridnik et al. 2021) with γ_neg=4, γ_pos=0, clip=0.05 — designed for long-tail multi-label classification, suppresses easy negatives so the model can attend to rare-class signal
- Regularization / training tricks: layer-wise learning rate decay (α=0.85), exponential moving average (β=0.999), **stochastic weight averaging** (last 25% of epochs), per-seed best-of-{base, EMA, SWA} selection on validation macro-F1, 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) (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 to ATT&CK techniques. The model takes a single sentence and outputs a probability for each of 50 techniques.

**Aggregation to document level:** per-sentence inference, take the per-class max across a document's sentences, threshold, report the union of predicted techniques per document.

**Threshold note:** the headline 77.17% uses a dev-tuned global threshold τ=0.59 selected on the held-out validation split (NOT on test). Using τ=0.5 uniform yields 76.87% on the same test set. See `results.json` for the full threshold-sweep curve.

**Limitations:**
- Trained on English-language CTI; behavior on other languages is not characterized.
- 50 TRAM2 sub-techniques only; sentences describing techniques outside this set produce all-zero predictions.
- The asymmetric loss is tuned for label-dense problems (mean ~82 samples/technique). For sparser benchmarks like AnnoCTR (mean 15.5/technique), the BCE configuration is preferable — see [`cassandra-bce-annoctr`](https://huggingface.co/cassandra-anon/cassandra-bce-annoctr) and the paper §3.2 (RQ4 results) for the label-density transfer analysis.

## 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.",
]
# τ=0.5 is the simplest threshold; for the headline 77.17% use τ=0.59
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 --threshold 0.59
```

## Per-seed members

| Seed | Tag | Per-document F1 (τ=0.5) | Selected weights |
|---|---|---|---|
| 42   | orig | 72.33% | SWA |
| 123  | orig | 74.72% | EMA |
| 456  | orig | 73.51% | base |
| 789  | repl | 71.31% | SWA |
| 2024 | repl | 70.35% | SWA |
| 3141 | repl | 69.81% | EMA |
| **6-seed ensemble (τ=0.5)** | — | **76.87%** | — |
| **6-seed ensemble (dev-τ=0.59)** | — | **77.17%** | — |

The "orig" / "repl" tag distinguishes the two 3-seed runs reported in the paper (originals and replication seeds for the per-seed variance study). For the headline 6-seed ensemble F1 they are pooled by averaging sigmoid probabilities.

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

## Citation

```bibtex
@misc{cassandra2026,
  title  = {CASSANDRA: How Many Parameters Suffice to Automate TTP Extractions from CTI Reports---Pushing Towards the Lower Bound},
  author = {{Anonymous Authors}},
  year   = {2026},
  note   = {Anonymous submission under review}
}
```

Please also cite TRAM2, the CTI-BERT encoder, and the asymmetric-loss work (Ridnik et al. 2021).

## License

Apache-2.0. These fine-tuned weights are derived from [`ibm-research/CTI-BERT`](https://huggingface.co/ibm-research/CTI-BERT).