PhishLens — Fine-tuned DistilBERT for Phishing Email Detection

A distilbert-base-uncased model fine-tuned to classify English email bodies as Safe (label 0) or Phishing (label 1).

This is the text agent of the PhishLens Chrome extension + FastAPI backend. The training notebooks and per-agent code live at PhishingDetector.

At a glance

Evaluated on a stratified 20% held-out test split of a deduplicated multi-source corpus of 29,555 emails (17,447 legit / 12,108 phishing).

How to use

from transformers import AutoTokenizer, AutoModelForSequenceClassification
import torch.nn.functional as F
import torch

MODEL = "Sonje03/phishlens-distilbert"

tok = AutoTokenizer.from_pretrained(MODEL)
model = AutoModelForSequenceClassification.from_pretrained(MODEL)
model.eval()

email = "Your account has been suspended. Click here to verify..."
inputs = tok(email, truncation=True, max_length=256, return_tensors="pt")
with torch.no_grad():
    probs = F.softmax(model(**inputs).logits, dim=-1)[0]
print(f"P(Safe)={probs[0]:.3f}   P(Phishing)={probs[1]:.3f}")

Training details

• Base model: distilbert-base-uncased (66M params)
• Epochs: 3
• Optimizer: AdamW, learning rate 2e-5
• Batch size: 16, mixed precision (FP16)
• Max sequence length: 256 tokens
• Hardware: single NVIDIA T4 GPU (Google Colab)

Training corpora

The augmented corpus dramatically lowers false positives on Nigerian-domain emails (banks, hospitals, telcos, university) that share template wording with phishing.

Intended use

Designed to be deployed behind the PhishLens FastAPI backend as one of three voting agents (text · URL · headers), with a trusted-domain allowlist that further reduces false positives on institutional senders.

Not intended for production phishing defence on its own — pair it with URL reputation services and DKIM/SPF/DMARC verification for any real deployment.

Limitations

• English-only. No support for French / Hausa / Yoruba phishing.
• PDF attachments are ignored. Only text/plain and text/html parts of an .eml are read.
• Niche marketing / recruitment false positives can still occur.

License

MIT.

Citation

@misc{phishlens2026,
  title  = {Smart Phishing Detection System Using Natural Language Processing Techniques},
  year   = {2026},
  school = {Nile University of Nigeria, Department of Cybersecurity},
  note   = {B.Sc. Final Year Project}
}