labs/Lab-3/Lab-3-Practical/04_Classification_Metrics_Lab.ipynb

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    "# Module 3 — Lab 4: Evaluate an Intrusion Classifier\n",
    "\n",
    "\n",
    "**Topics:** confusion matrix, accuracy, precision, recall, F1-score, error analysis\n",
    "\n",
    "> **Instructions:** Run the cells in order. Complete every `TODO`, then run the **Self-check** cell. Do not open the Solution notebook before attempting the tasks yourself.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "04669dcb",
   "metadata": {},
   "source": [
    "## Learning objectives\n",
    "\n",
    "After completing this lab, you will be able to:\n",
    "\n",
    "- calculate a confusion matrix and classification metrics;\n",
    "- distinguish false positives from false negatives;\n",
    "- explain why attack recall matters in intrusion detection;\n",
    "- inspect misclassified network flows.\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "f78f254b",
   "metadata": {},
   "outputs": [],
   "source": [
    "from pathlib import Path\n",
    "import numpy as np\n",
    "import pandas as pd\n",
    "\n",
    "DATA_PATH = Path(\"data/cicids2017_binary_sample.csv\")\n",
    "RANDOM_STATE = 42\n",
    "\n",
    "import matplotlib.pyplot as plt\n",
    "from sklearn.model_selection import train_test_split\n",
    "from sklearn.pipeline import Pipeline\n",
    "from sklearn.impute import SimpleImputer\n",
    "from sklearn.ensemble import RandomForestClassifier\n",
    "from sklearn.metrics import (\n",
    "    ConfusionMatrixDisplay, accuracy_score, classification_report,\n",
    "    confusion_matrix, precision_score, recall_score, f1_score\n",
    ")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "b9399f00",
   "metadata": {},
   "source": [
    "## 1. Train the baseline pipeline\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "4e0967ef",
   "metadata": {},
   "outputs": [],
   "source": [
    "df = pd.read_csv(DATA_PATH).drop_duplicates()\n",
    "df.columns = df.columns.str.strip()\n",
    "df = df.replace([np.inf, -np.inf], np.nan)\n",
    "\n",
    "X = df.drop(columns=\"Label\").select_dtypes(include=\"number\")\n",
    "y = df[\"Label\"].astype(str).str.strip().str.upper().ne(\"BENIGN\").astype(int)\n",
    "\n",
    "X_train, X_test, y_train, y_test = train_test_split(\n",
    "    X, y, test_size=0.2, random_state=RANDOM_STATE, stratify=y\n",
    ")\n",
    "\n",
    "pipeline = Pipeline([\n",
    "    (\"imputer\", SimpleImputer(strategy=\"median\")),\n",
    "    (\"model\", RandomForestClassifier(\n",
    "        n_estimators=100, max_depth=12,\n",
    "        random_state=RANDOM_STATE, n_jobs=-1\n",
    "    )),\n",
    "])\n",
    "\n",
    "# TODO 1: fit the pipeline and create y_pred\n",
    "y_pred = None\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "b83691ce",
   "metadata": {},
   "source": [
    "## 2. Calculate the confusion matrix\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "2e6d0759",
   "metadata": {},
   "outputs": [],
   "source": [
    "# TODO 2: calculate the confusion matrix and unpack tn, fp, fn, tp\n",
    "cm = None\n",
    "tn, fp, fn, tp = None, None, None, None\n",
    "\n",
    "print(\"Confusion matrix:\\n\", cm)\n",
    "print(f\"TN={tn}, FP={fp}, FN={fn}, TP={tp}\")\n",
    "\n",
    "# TODO 3: display the confusion matrix with class names BENIGN and ATTACK\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e410267b",
   "metadata": {},
   "source": [
    "## 3. Calculate classification metrics\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "2bb935f4",
   "metadata": {},
   "outputs": [],
   "source": [
    "# TODO 4: calculate accuracy, attack precision, attack recall, and attack F1\n",
    "accuracy = None\n",
    "attack_precision = None\n",
    "attack_recall = None\n",
    "attack_f1 = None\n",
    "\n",
    "metrics = pd.Series({\n",
    "    \"accuracy\": accuracy,\n",
    "    \"attack_precision\": attack_precision,\n",
    "    \"attack_recall\": attack_recall,\n",
    "    \"attack_f1\": attack_f1,\n",
    "})\n",
    "print(metrics.round(3))\n",
    "\n",
    "# TODO 5: print classification_report with BENIGN and ATTACK target names\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "c2719c46",
   "metadata": {},
   "source": [
    "## 4. Inspect false negatives\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "9b14d27c",
   "metadata": {},
   "outputs": [],
   "source": [
    "results = X_test.copy()\n",
    "results[\"actual\"] = y_test\n",
    "results[\"predicted\"] = y_pred\n",
    "\n",
    "# TODO 6: retain rows where actual is ATTACK and predicted is BENIGN\n",
    "false_negatives = None\n",
    "\n",
    "print(\"False negatives:\", None)\n",
    "false_negatives.head()\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "9383f9fa",
   "metadata": {},
   "source": [
    "## Self-check\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "21628fcf",
   "metadata": {},
   "outputs": [],
   "source": [
    "assert cm.shape == (2, 2)\n",
    "assert tn + fp + fn + tp == len(y_test)\n",
    "assert 0 <= accuracy <= 1\n",
    "assert 0 <= attack_precision <= 1\n",
    "assert 0 <= attack_recall <= 1\n",
    "assert 0 <= attack_f1 <= 1\n",
    "assert len(false_negatives) == fn\n",
    "print(\"✓ Lab 4 completed\")\n"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e2f95d64",
   "metadata": {},
   "source": [
    "## Analyst questions\n",
    "\n",
    "1. Which confusion-matrix cell represents a missed attack?\n",
    "2. Which metric should receive more attention if missed attacks are very costly?\n",
    "3. Why can improving attack recall increase the number of false alerts?\n"
   ]
  }
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