Initial commit

Utility/extractBehaviourFeatures.js

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+function extractBehaviourFeatures(actions) {
+  if (!actions || actions.length < 2) return null;
+
+  const actionCounts = {};
+  const idleThreshold = 5000;
+  const windowSize = 5;
+  const intervals = [];
+  const sequenceBuffer = [];
+  let totalInterval = 0;
+  let minInterval = Infinity;
+  let maxInterval = -Infinity;
+  let idleTimeCount = 0;
+  let idleTimeTotal = 0;
+  let lastTimestamp = actions[0].timestamp;
+  let prevAction = actions[0].opcode;
+  let sequenceMap = {};
+
+  for (let i = 1; i < actions.length; i++) {
+    const current = actions[i];
+    const interval = current.timestamp - lastTimestamp;
+    lastTimestamp = current.timestamp;
+
+    intervals.push(interval);
+
+    totalInterval += interval;
+    minInterval = Math.min(minInterval, interval);
+    maxInterval = Math.max(maxInterval, interval);
+
+    actionCounts[current.opcode] = (actionCounts[current.opcode] || 0) + 1;
+
+    if (interval > idleThreshold) {
+      idleTimeCount++;
+      idleTimeTotal += interval;
+    };
+
+    sequenceBuffer.push(current.opcode);
+    if (sequenceBuffer.length === windowSize) {
+      const key = sequenceBuffer.join(",");
+      sequenceMap[key] = (sequenceMap[key] || 0) + 1;
+
+      sequenceBuffer.shift();
+    };
+
+    prevAction = current.opcode;
+  };
+
+  const meanInterval = totalInterval / intervals.length;
+  const stdDevInterval = Math.sqrt(intervals.reduce((sum, val) => sum + (val - meanInterval) ** 2, 0) / intervals.length);
+
+  const uniqueActionsCount = Object.keys(actionCounts).length;
+  const idleTimeRatio = idleTimeCount / (actions.length - 1);
+  const maxSequenceRepeats = Math.max(...Object.values(sequenceMap)) || 0;
+
+  const totalActions = actions.length;
+  let entropy = 0;
+
+  for (const count of Object.values(actionCounts)) {
+    const p = count / totalActions;
+    entropy -= p * Math.log2(p);
+  };
+
+  return {
+    timestamp: new Date(),
+    timestampStart: null,
+    meanInterval,
+    stdDevInterval,
+    minInterval,
+    maxInterval,
+    uniqueActionsCount,
+    actionEntropy: entropy,
+    maxSequenceRepeats,
+    idleTimeRatio
+  };
+};
+
+module.exports = extractBehaviourFeatures;