feat: add human detection scoring and webhook notifications

Implement phase 2.1 (human detection) and 2.2 (notifications): - Detection scorer computes 0.0-1.0 human likelihood from keystroke timing variance, special key usage, typing speed, command diversity, and session duration - Webhook notifier sends JSON POST to configured endpoints with deduplication, custom headers, and event filtering - RecordingChannel gains an event callback for feeding keystrokes to the scorer without coupling shell and detection packages - Server wires scorer into session lifecycle with periodic updates and threshold-based notification triggers - Web UI shows human score in session tables with highlighting - New config sections: [detection] and [[notify.webhooks]] Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-14 21:28:11 +01:00
parent 96c8476f77
commit 0ad6f4cb6a
13 changed files with 1060 additions and 32 deletions
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -9,13 +9,15 @@ import (
 )

 type Config struct {
-	SSH       SSHConfig      `toml:"ssh"`
-	Auth      AuthConfig     `toml:"auth"`
-	Storage   StorageConfig  `toml:"storage"`
-	Shell     ShellConfig    `toml:"shell"`
-	Web       WebConfig      `toml:"web"`
-	LogLevel  string         `toml:"log_level"`
-	LogFormat string         `toml:"log_format"` // "text" (default) or "json"
+	SSH       SSHConfig       `toml:"ssh"`
+	Auth      AuthConfig      `toml:"auth"`
+	Storage   StorageConfig   `toml:"storage"`
+	Shell     ShellConfig     `toml:"shell"`
+	Web       WebConfig       `toml:"web"`
+	Detection DetectionConfig `toml:"detection"`
+	Notify    NotifyConfig    `toml:"notify"`
+	LogLevel  string          `toml:"log_level"`
+	LogFormat string          `toml:"log_format"` // "text" (default) or "json"
 }

 type WebConfig struct {
@@ -59,6 +61,25 @@ type Credential struct {
 	Password string `toml:"password"`
 }

+type DetectionConfig struct {
+	Enabled        bool    `toml:"enabled"`
+	Threshold      float64 `toml:"threshold"`
+	UpdateInterval string  `toml:"update_interval"`
+
+	// Parsed duration, not from TOML directly.
+	UpdateIntervalDuration time.Duration `toml:"-"`
+}
+
+type NotifyConfig struct {
+	Webhooks []WebhookNotifyConfig `toml:"webhooks"`
+}
+
+type WebhookNotifyConfig struct {
+	URL     string            `toml:"url"`
+	Headers map[string]string `toml:"headers"`
+	Events  []string          `toml:"events"` // empty = all events
+}
+
 func Load(path string) (*Config, error) {
 	data, err := os.ReadFile(path)
 	if err != nil {
@@ -127,6 +148,12 @@ func applyDefaults(cfg *Config) {
 	if cfg.Shell.Banner == "" {
 		cfg.Shell.Banner = "Welcome to Ubuntu 22.04.3 LTS (GNU/Linux 5.15.0-89-generic x86_64)\r\n\r\n"
 	}
+	if cfg.Detection.Threshold == 0 {
+		cfg.Detection.Threshold = 0.6
+	}
+	if cfg.Detection.UpdateInterval == "" {
+		cfg.Detection.UpdateInterval = "5s"
+	}
 }

 // knownShellKeys are top-level keys in [shell] that are not per-shell sub-tables.
@@ -189,5 +216,33 @@ func validate(cfg *Config) error {
 		}
 	}

+	// Validate detection config.
+	if cfg.Detection.Enabled {
+		if cfg.Detection.Threshold < 0 || cfg.Detection.Threshold > 1 {
+			return fmt.Errorf("detection.threshold must be between 0 and 1, got %f", cfg.Detection.Threshold)
+		}
+		ui, err := time.ParseDuration(cfg.Detection.UpdateInterval)
+		if err != nil {
+			return fmt.Errorf("invalid detection.update_interval %q: %w", cfg.Detection.UpdateInterval, err)
+		}
+		if ui <= 0 {
+			return fmt.Errorf("detection.update_interval must be positive, got %s", ui)
+		}
+		cfg.Detection.UpdateIntervalDuration = ui
+	}
+
+	// Validate notify config.
+	knownEvents := map[string]bool{"human_detected": true, "session_started": true}
+	for i, wh := range cfg.Notify.Webhooks {
+		if wh.URL == "" {
+			return fmt.Errorf("notify.webhooks[%d]: url must not be empty", i)
+		}
+		for j, ev := range wh.Events {
+			if !knownEvents[ev] {
+				return fmt.Errorf("notify.webhooks[%d].events[%d]: unknown event %q", i, j, ev)
+			}
+		}
+	}
+
 	return nil
 }
--- a/internal/detection/scorer.go
+++ b/internal/detection/scorer.go
@@ -0,0 +1,259 @@
+package detection
+
+import (
+	"math"
+	"sync"
+	"time"
+)
+
+// Direction constants for RecordEvent.
+const (
+	DirInput  = 0 // client → server (keystrokes)
+	DirOutput = 1 // server → client (shell output)
+)
+
+// Signal weights for the composite score.
+const (
+	weightTimingVariance  = 0.30
+	weightSpecialKeys     = 0.20
+	weightTypingSpeed     = 0.20
+	weightCommandDiversity = 0.15
+	weightSessionDuration = 0.15
+)
+
+// Scorer accumulates keystroke events and computes a 0.0–1.0
+// human likelihood score based on multiple signals.
+type Scorer struct {
+	mu sync.Mutex
+
+	// Input timing data.
+	inputTimes []time.Time
+	delays     []time.Duration
+
+	// Special key counters.
+	specialKeys int
+
+	// Command tracking: we count newlines and unique command prefixes.
+	currentCmd []byte
+	commands   map[string]struct{}
+
+	// Session activity duration.
+	firstInput time.Time
+	lastInput  time.Time
+}
+
+// NewScorer returns a new Scorer ready to record events.
+func NewScorer() *Scorer {
+	return &Scorer{
+		commands: make(map[string]struct{}),
+	}
+}
+
+// RecordEvent records a data event with timestamp and direction.
+// direction should be DirInput (0) for client input or DirOutput (1) for server output.
+func (s *Scorer) RecordEvent(ts time.Time, direction int, data []byte) {
+	if direction != DirInput {
+		return // only analyze input
+	}
+
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if s.firstInput.IsZero() {
+		s.firstInput = ts
+	}
+	s.lastInput = ts
+
+	for _, b := range data {
+		// Track inter-keystroke delay for single-byte inputs.
+		if len(s.inputTimes) > 0 {
+			delay := ts.Sub(s.inputTimes[len(s.inputTimes)-1])
+			if delay > 0 && delay < 30*time.Second {
+				s.delays = append(s.delays, delay)
+			}
+		}
+		s.inputTimes = append(s.inputTimes, ts)
+
+		// Count special keys.
+		if isSpecialKey(b) {
+			s.specialKeys++
+		}
+
+		// Track commands (split on newline/CR).
+		if b == '\r' || b == '\n' {
+			cmd := string(s.currentCmd)
+			if len(cmd) > 0 {
+				s.commands[cmd] = struct{}{}
+			}
+			s.currentCmd = s.currentCmd[:0]
+		} else {
+			// Handle backspace: remove last byte from current command.
+			if b == 0x7f || b == 0x08 {
+				if len(s.currentCmd) > 0 {
+					s.currentCmd = s.currentCmd[:len(s.currentCmd)-1]
+				}
+			} else if b >= 0x20 { // printable
+				s.currentCmd = append(s.currentCmd, b)
+			}
+		}
+	}
+}
+
+// Score computes the composite human likelihood score (0.0–1.0).
+// Thread-safe.
+func (s *Scorer) Score() float64 {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
+	if len(s.inputTimes) == 0 {
+		return 0
+	}
+
+	tv := s.timingVarianceScore()
+	sk := s.specialKeysScore()
+	ts := s.typingSpeedScore()
+	cd := s.commandDiversityScore()
+	sd := s.sessionDurationScore()
+
+	score := tv*weightTimingVariance +
+		sk*weightSpecialKeys +
+		ts*weightTypingSpeed +
+		cd*weightCommandDiversity +
+		sd*weightSessionDuration
+
+	return clamp(score, 0, 1)
+}
+
+// timingVarianceScore returns 0–1 based on coefficient of variation of inter-key delays.
+// Bots have CV ≈ 0 (instant or uniform), humans have CV ≥ 0.6.
+func (s *Scorer) timingVarianceScore() float64 {
+	if len(s.delays) < 3 {
+		return 0
+	}
+
+	mean := meanDuration(s.delays)
+	if mean == 0 {
+		return 0
+	}
+
+	variance := 0.0
+	for _, d := range s.delays {
+		diff := float64(d) - float64(mean)
+		variance += diff * diff
+	}
+	variance /= float64(len(s.delays))
+	stddev := math.Sqrt(variance)
+	cv := stddev / float64(mean)
+
+	// Map CV to 0–1: CV of 0.6+ is fully human-like.
+	return clamp(cv/0.6, 0, 1)
+}
+
+// specialKeysScore returns 0–1 based on count of special key presses.
+// Scripts almost never generate backspace/tab/ctrl characters.
+func (s *Scorer) specialKeysScore() float64 {
+	// 5+ special keys → full score.
+	return clamp(float64(s.specialKeys)/5.0, 0, 1)
+}
+
+// typingSpeedScore returns 0–1 based on median inter-key delay.
+// Paste/scripts have < 5ms, humans have 30–300ms.
+func (s *Scorer) typingSpeedScore() float64 {
+	if len(s.delays) < 2 {
+		return 0
+	}
+
+	med := medianDuration(s.delays)
+	ms := float64(med) / float64(time.Millisecond)
+
+	if ms < 5 {
+		return 0 // paste or script
+	}
+	if ms > 300 {
+		return 0.7 // very slow, still possibly human
+	}
+	if ms >= 30 && ms <= 300 {
+		return 1.0 // human range
+	}
+	// 5–30ms: transition zone
+	return clamp((ms-5)/25, 0, 1)
+}
+
+// commandDiversityScore returns 0–1 based on number of unique commands.
+func (s *Scorer) commandDiversityScore() float64 {
+	// 3+ unique commands → full score.
+	return clamp(float64(len(s.commands))/3.0, 0, 1)
+}
+
+// sessionDurationScore returns 0–1 based on active input duration.
+func (s *Scorer) sessionDurationScore() float64 {
+	if s.firstInput.IsZero() || s.lastInput.IsZero() {
+		return 0
+	}
+	dur := s.lastInput.Sub(s.firstInput)
+	// 10s+ of active input → full score.
+	return clamp(float64(dur)/float64(10*time.Second), 0, 1)
+}
+
+// isSpecialKey returns true for non-printable keys that humans commonly use.
+func isSpecialKey(b byte) bool {
+	switch b {
+	case 0x7f, // DEL (backspace in most terminals)
+		0x08, // BS
+		0x09, // TAB
+		0x03, // Ctrl-C
+		0x04, // Ctrl-D
+		0x1b: // ESC (arrow keys start with ESC)
+		return true
+	}
+	return false
+}
+
+func clamp(v, lo, hi float64) float64 {
+	if v < lo {
+		return lo
+	}
+	if v > hi {
+		return hi
+	}
+	return v
+}
+
+func meanDuration(ds []time.Duration) time.Duration {
+	if len(ds) == 0 {
+		return 0
+	}
+	var sum time.Duration
+	for _, d := range ds {
+		sum += d
+	}
+	return sum / time.Duration(len(ds))
+}
+
+func medianDuration(ds []time.Duration) time.Duration {
+	n := len(ds)
+	if n == 0 {
+		return 0
+	}
+	// Copy to avoid mutating the original.
+	sorted := make([]time.Duration, n)
+	copy(sorted, ds)
+	sortDurations(sorted)
+	if n%2 == 0 {
+		return (sorted[n/2-1] + sorted[n/2]) / 2
+	}
+	return sorted[n/2]
+}
+
+func sortDurations(ds []time.Duration) {
+	// Simple insertion sort — delay slices are small.
+	for i := 1; i < len(ds); i++ {
+		key := ds[i]
+		j := i - 1
+		for j >= 0 && ds[j] > key {
+			ds[j+1] = ds[j]
+			j--
+		}
+		ds[j+1] = key
+	}
+}
--- a/internal/detection/scorer_test.go
+++ b/internal/detection/scorer_test.go
@@ -0,0 +1,155 @@
+package detection
+
+import (
+	"sync"
+	"testing"
+	"time"
+)
+
+func TestScorer_EmptyInput(t *testing.T) {
+	s := NewScorer()
+	score := s.Score()
+	if score != 0 {
+		t.Errorf("empty scorer: got %f, want 0", score)
+	}
+}
+
+func TestScorer_SingleKeystroke(t *testing.T) {
+	s := NewScorer()
+	s.RecordEvent(time.Now(), DirInput, []byte("a"))
+	score := s.Score()
+	if score != 0 {
+		t.Errorf("single keystroke: got %f, want 0", score)
+	}
+}
+
+func TestScorer_BotLikeInput(t *testing.T) {
+	// Simulate a bot: paste entire commands with uniform tiny delays, no special keys.
+	s := NewScorer()
+	now := time.Now()
+
+	// Bot pastes "cat /etc/passwd\r" all at once with perfectly uniform timing.
+	for range 3 {
+		cmd := []byte("cat /etc/passwd\r")
+		for _, b := range cmd {
+			s.RecordEvent(now, DirInput, []byte{b})
+			now = now.Add(100 * time.Microsecond) // ~0.1ms uniform delay = paste
+		}
+	}
+
+	score := s.Score()
+	if score >= 0.3 {
+		t.Errorf("bot-like input: got %f, want < 0.3", score)
+	}
+}
+
+func TestScorer_HumanLikeInput(t *testing.T) {
+	// Simulate a human: variable timing, backspaces, diverse commands.
+	s := NewScorer()
+	now := time.Now()
+
+	type cmd struct {
+		text  string
+		delay time.Duration // base delay between keys
+	}
+
+	commands := []cmd{
+		{"ls -la\r", 80 * time.Millisecond},
+		{"cat /etc/paswd", 120 * time.Millisecond}, // typo
+		{string([]byte{0x7f}), 200 * time.Millisecond},  // backspace
+		{"wd\r", 90 * time.Millisecond},                  // correction
+		{"whoami\r", 100 * time.Millisecond},
+		{"uname -a\r", 150 * time.Millisecond},
+		{string([]byte{0x09}), 300 * time.Millisecond}, // tab completion
+		{"pwd\r", 70 * time.Millisecond},
+	}
+
+	for _, c := range commands {
+		for _, b := range []byte(c.text) {
+			// Add ±30% jitter to make timing more natural.
+			jitter := time.Duration(float64(c.delay) * 0.3)
+			delay := c.delay + jitter // simplified: always add, still variable across commands
+			s.RecordEvent(now, DirInput, []byte{b})
+			now = now.Add(delay)
+		}
+		// Pause between commands (thinking time).
+		now = now.Add(2 * time.Second)
+	}
+
+	score := s.Score()
+	if score <= 0.6 {
+		t.Errorf("human-like input: got %f, want > 0.6", score)
+	}
+}
+
+func TestScorer_OutputIgnored(t *testing.T) {
+	s := NewScorer()
+	now := time.Now()
+
+	// Only output events — should not affect score.
+	for i := 0; i < 100; i++ {
+		s.RecordEvent(now, DirOutput, []byte("some output\n"))
+		now = now.Add(10 * time.Millisecond)
+	}
+
+	score := s.Score()
+	if score != 0 {
+		t.Errorf("output-only: got %f, want 0", score)
+	}
+}
+
+func TestScorer_ThreadSafety(t *testing.T) {
+	s := NewScorer()
+	now := time.Now()
+
+	var wg sync.WaitGroup
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func(offset int) {
+			defer wg.Done()
+			for j := 0; j < 100; j++ {
+				ts := now.Add(time.Duration(offset*100+j) * time.Millisecond)
+				s.RecordEvent(ts, DirInput, []byte("a"))
+			}
+		}(i)
+	}
+
+	// Concurrently read score.
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for i := 0; i < 50; i++ {
+			_ = s.Score()
+		}
+	}()
+
+	wg.Wait()
+
+	// Should not panic; score should be valid.
+	score := s.Score()
+	if score < 0 || score > 1 {
+		t.Errorf("concurrent score out of range: %f", score)
+	}
+}
+
+func TestScorer_CommandDiversity(t *testing.T) {
+	s := NewScorer()
+	now := time.Now()
+
+	// Type 4 different commands with human-ish timing.
+	cmds := []string{"ls\r", "pwd\r", "id\r", "whoami\r"}
+	for _, cmd := range cmds {
+		for _, b := range []byte(cmd) {
+			s.RecordEvent(now, DirInput, []byte{b})
+			now = now.Add(100 * time.Millisecond)
+		}
+		now = now.Add(time.Second)
+	}
+
+	score := s.Score()
+	// With 4 unique commands, human timing, and decent duration,
+	// we should get a meaningful score.
+	if score < 0.4 {
+		t.Errorf("diverse commands: got %f, want >= 0.4", score)
+	}
+}
--- a/internal/notify/webhook.go
+++ b/internal/notify/webhook.go
@@ -0,0 +1,179 @@
+package notify
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"sync"
+	"time"
+
+	"git.t-juice.club/torjus/oubliette/internal/config"
+)
+
+// Event types.
+const (
+	EventHumanDetected  = "human_detected"
+	EventSessionStarted = "session_started"
+)
+
+// SessionInfo holds session data included in webhook payloads.
+type SessionInfo struct {
+	ID          string   `json:"id"`
+	IP          string   `json:"ip"`
+	Username    string   `json:"username"`
+	ShellName   string   `json:"shell_name"`
+	HumanScore  float64  `json:"human_score"`
+	ConnectedAt string   `json:"connected_at"`
+}
+
+// webhookPayload is the JSON body sent to webhooks.
+type webhookPayload struct {
+	Event     string      `json:"event"`
+	Timestamp string      `json:"timestamp"`
+	Session   SessionInfo `json:"session"`
+}
+
+// Notifier sends webhook notifications for honeypot events.
+type Notifier struct {
+	webhooks []config.WebhookNotifyConfig
+	logger   *slog.Logger
+	client   *http.Client
+
+	mu   sync.Mutex
+	sent map[string]struct{} // dedup key: "sessionID:eventType"
+}
+
+// NewNotifier creates a Notifier with the given webhook configurations.
+func NewNotifier(webhooks []config.WebhookNotifyConfig, logger *slog.Logger) *Notifier {
+	return &Notifier{
+		webhooks: webhooks,
+		logger:   logger,
+		client:   &http.Client{Timeout: 10 * time.Second},
+		sent:     make(map[string]struct{}),
+	}
+}
+
+// Notify sends a notification for the given event type and session.
+// Deduplicates by (sessionID, eventType) — each combination is sent at most once.
+func (n *Notifier) Notify(ctx context.Context, eventType string, session SessionInfo) {
+	dedupKey := session.ID + ":" + eventType
+
+	n.mu.Lock()
+	if _, ok := n.sent[dedupKey]; ok {
+		n.mu.Unlock()
+		return
+	}
+	n.sent[dedupKey] = struct{}{}
+	n.mu.Unlock()
+
+	payload := webhookPayload{
+		Event:     eventType,
+		Timestamp: time.Now().UTC().Format(time.RFC3339),
+		Session:   session,
+	}
+
+	for _, wh := range n.webhooks {
+		if !n.shouldSend(wh, eventType) {
+			continue
+		}
+		go n.send(ctx, wh, payload)
+	}
+}
+
+// CleanupSession removes dedup state for a session.
+func (n *Notifier) CleanupSession(sessionID string) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	for key := range n.sent {
+		if len(key) > len(sessionID) && key[:len(sessionID)+1] == sessionID+":" {
+			delete(n.sent, key)
+		}
+	}
+}
+
+// shouldSend returns true if the webhook is configured to receive this event type.
+func (n *Notifier) shouldSend(wh config.WebhookNotifyConfig, eventType string) bool {
+	if len(wh.Events) == 0 {
+		return true // empty = all events
+	}
+	for _, ev := range wh.Events {
+		if ev == eventType {
+			return true
+		}
+	}
+	return false
+}
+
+func (n *Notifier) send(ctx context.Context, wh config.WebhookNotifyConfig, payload webhookPayload) {
+	body, err := json.Marshal(payload)
+	if err != nil {
+		n.logger.Error("failed to marshal webhook payload", "err", err)
+		return
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, wh.URL, bytes.NewReader(body))
+	if err != nil {
+		n.logger.Error("failed to create webhook request", "err", err, "url", wh.URL)
+		return
+	}
+
+	req.Header.Set("Content-Type", "application/json")
+	for k, v := range wh.Headers {
+		req.Header.Set(k, v)
+	}
+
+	resp, err := n.client.Do(req)
+	if err != nil {
+		n.logger.Error("webhook request failed", "err", err, "url", wh.URL)
+		return
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode >= 400 {
+		n.logger.Warn("webhook returned error status",
+			"url", wh.URL,
+			"status", resp.StatusCode,
+			"event", payload.Event,
+		)
+		return
+	}
+
+	n.logger.Debug("webhook sent",
+		"url", wh.URL,
+		"event", payload.Event,
+		"session_id", payload.Session.ID,
+	)
+}
+
+// FormatConnectedAt formats a time for use in SessionInfo.
+func FormatConnectedAt(t time.Time) string {
+	return t.UTC().Format(time.RFC3339)
+}
+
+// NoopNotifier is a no-op notifier used when no webhooks are configured.
+type NoopNotifier struct{}
+
+func (NoopNotifier) Notify(context.Context, string, SessionInfo) {}
+func (NoopNotifier) CleanupSession(string)                       {}
+
+// Sender is the interface for sending notifications.
+type Sender interface {
+	Notify(ctx context.Context, eventType string, session SessionInfo)
+	CleanupSession(sessionID string)
+}
+
+var (
+	_ Sender = (*Notifier)(nil)
+	_ Sender = NoopNotifier{}
+)
+
+// NewSender creates a Sender from configuration. Returns a NoopNotifier
+// if no webhooks are configured.
+func NewSender(webhooks []config.WebhookNotifyConfig, logger *slog.Logger) Sender {
+	if len(webhooks) == 0 {
+		return NoopNotifier{}
+	}
+	return NewNotifier(webhooks, logger)
+}
--- a/internal/notify/webhook_test.go
+++ b/internal/notify/webhook_test.go
@@ -0,0 +1,243 @@
+package notify
+
+import (
+	"context"
+	"encoding/json"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+
+	"git.t-juice.club/torjus/oubliette/internal/config"
+)
+
+func testSession() SessionInfo {
+	return SessionInfo{
+		ID:          "test-session-123",
+		IP:          "1.2.3.4",
+		Username:    "root",
+		ShellName:   "bash",
+		HumanScore:  0.85,
+		ConnectedAt: FormatConnectedAt(time.Now()),
+	}
+}
+
+func TestNotifier_PayloadStructure(t *testing.T) {
+	var received webhookPayload
+	var mu sync.Mutex
+	done := make(chan struct{})
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		defer mu.Unlock()
+		if err := json.NewDecoder(r.Body).Decode(&received); err != nil {
+			t.Errorf("failed to decode payload: %v", err)
+		}
+		w.WriteHeader(http.StatusOK)
+		close(done)
+	}))
+	defer srv.Close()
+
+	webhooks := []config.WebhookNotifyConfig{
+		{URL: srv.URL},
+	}
+
+	n := NewNotifier(webhooks, slog.Default())
+	session := testSession()
+	n.Notify(context.Background(), EventHumanDetected, session)
+
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for webhook")
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+	if received.Event != EventHumanDetected {
+		t.Errorf("event: got %q, want %q", received.Event, EventHumanDetected)
+	}
+	if received.Session.ID != session.ID {
+		t.Errorf("session ID: got %q, want %q", received.Session.ID, session.ID)
+	}
+	if received.Session.IP != session.IP {
+		t.Errorf("session IP: got %q, want %q", received.Session.IP, session.IP)
+	}
+	if received.Session.HumanScore != session.HumanScore {
+		t.Errorf("score: got %f, want %f", received.Session.HumanScore, session.HumanScore)
+	}
+	if received.Timestamp == "" {
+		t.Error("timestamp should not be empty")
+	}
+}
+
+func TestNotifier_CustomHeaders(t *testing.T) {
+	var receivedHeaders http.Header
+	done := make(chan struct{})
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		receivedHeaders = r.Header.Clone()
+		w.WriteHeader(http.StatusOK)
+		close(done)
+	}))
+	defer srv.Close()
+
+	webhooks := []config.WebhookNotifyConfig{
+		{
+			URL: srv.URL,
+			Headers: map[string]string{
+				"Authorization": "Bearer test-token",
+				"X-Custom":      "my-value",
+			},
+		},
+	}
+
+	n := NewNotifier(webhooks, slog.Default())
+	n.Notify(context.Background(), EventSessionStarted, testSession())
+
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timeout waiting for webhook")
+	}
+
+	if got := receivedHeaders.Get("Authorization"); got != "Bearer test-token" {
+		t.Errorf("Authorization header: got %q, want %q", got, "Bearer test-token")
+	}
+	if got := receivedHeaders.Get("X-Custom"); got != "my-value" {
+		t.Errorf("X-Custom header: got %q, want %q", got, "my-value")
+	}
+	if got := receivedHeaders.Get("Content-Type"); got != "application/json" {
+		t.Errorf("Content-Type: got %q, want %q", got, "application/json")
+	}
+}
+
+func TestNotifier_Deduplication(t *testing.T) {
+	var count int
+	var mu sync.Mutex
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		count++
+		mu.Unlock()
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer srv.Close()
+
+	webhooks := []config.WebhookNotifyConfig{{URL: srv.URL}}
+	n := NewNotifier(webhooks, slog.Default())
+	session := testSession()
+
+	// Send same event three times for the same session.
+	for range 3 {
+		n.Notify(context.Background(), EventHumanDetected, session)
+	}
+
+	// Allow goroutines to complete.
+	time.Sleep(500 * time.Millisecond)
+
+	mu.Lock()
+	defer mu.Unlock()
+	if count != 1 {
+		t.Errorf("dedup: got %d sends, want 1", count)
+	}
+}
+
+func TestNotifier_EventFiltering(t *testing.T) {
+	var receivedEvents []string
+	var mu sync.Mutex
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var payload webhookPayload
+		_ = json.NewDecoder(r.Body).Decode(&payload)
+		mu.Lock()
+		receivedEvents = append(receivedEvents, payload.Event)
+		mu.Unlock()
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer srv.Close()
+
+	// Only subscribe to human_detected.
+	webhooks := []config.WebhookNotifyConfig{
+		{
+			URL:    srv.URL,
+			Events: []string{EventHumanDetected},
+		},
+	}
+
+	n := NewNotifier(webhooks, slog.Default())
+	session := testSession()
+
+	// Send both event types.
+	n.Notify(context.Background(), EventSessionStarted, session)
+	// Need a different session for human_detected to avoid dedup with same session.
+	session2 := testSession()
+	session2.ID = "test-session-456"
+	n.Notify(context.Background(), EventHumanDetected, session2)
+
+	time.Sleep(500 * time.Millisecond)
+
+	mu.Lock()
+	defer mu.Unlock()
+	if len(receivedEvents) != 1 {
+		t.Fatalf("event filtering: got %d events, want 1", len(receivedEvents))
+	}
+	if receivedEvents[0] != EventHumanDetected {
+		t.Errorf("filtered event: got %q, want %q", receivedEvents[0], EventHumanDetected)
+	}
+}
+
+func TestNotifier_CleanupSession(t *testing.T) {
+	var count int
+	var mu sync.Mutex
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		mu.Lock()
+		count++
+		mu.Unlock()
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer srv.Close()
+
+	webhooks := []config.WebhookNotifyConfig{{URL: srv.URL}}
+	n := NewNotifier(webhooks, slog.Default())
+	session := testSession()
+
+	n.Notify(context.Background(), EventHumanDetected, session)
+	time.Sleep(200 * time.Millisecond)
+
+	// Cleanup and resend — should work again.
+	n.CleanupSession(session.ID)
+	n.Notify(context.Background(), EventHumanDetected, session)
+	time.Sleep(200 * time.Millisecond)
+
+	mu.Lock()
+	defer mu.Unlock()
+	if count != 2 {
+		t.Errorf("after cleanup: got %d sends, want 2", count)
+	}
+}
+
+func TestNoopNotifier(t *testing.T) {
+	// Should not panic.
+	n := NoopNotifier{}
+	n.Notify(context.Background(), EventHumanDetected, testSession())
+	n.CleanupSession("test")
+}
+
+func TestNewSender_NoWebhooks(t *testing.T) {
+	sender := NewSender(nil, slog.Default())
+	if _, ok := sender.(NoopNotifier); !ok {
+		t.Errorf("expected NoopNotifier, got %T", sender)
+	}
+}
+
+func TestNewSender_WithWebhooks(t *testing.T) {
+	webhooks := []config.WebhookNotifyConfig{{URL: "http://example.com"}}
+	sender := NewSender(webhooks, slog.Default())
+	if _, ok := sender.(*Notifier); !ok {
+		t.Errorf("expected *Notifier, got %T", sender)
+	}
+}
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -14,6 +14,8 @@ import (

 	"git.t-juice.club/torjus/oubliette/internal/auth"
 	"git.t-juice.club/torjus/oubliette/internal/config"
+	"git.t-juice.club/torjus/oubliette/internal/detection"
+	"git.t-juice.club/torjus/oubliette/internal/notify"
 	"git.t-juice.club/torjus/oubliette/internal/shell"
 	"git.t-juice.club/torjus/oubliette/internal/shell/bash"
 	"git.t-juice.club/torjus/oubliette/internal/storage"
@@ -21,13 +23,14 @@ import (
 )

 type Server struct {
-	cfg            config.Config
-	store          storage.Store
-	authenticator  *auth.Authenticator
-	sshConfig      *ssh.ServerConfig
-	logger         *slog.Logger
-	connSem        chan struct{} // semaphore limiting concurrent connections
-	shellRegistry  *shell.Registry
+	cfg           config.Config
+	store         storage.Store
+	authenticator *auth.Authenticator
+	sshConfig     *ssh.ServerConfig
+	logger        *slog.Logger
+	connSem       chan struct{} // semaphore limiting concurrent connections
+	shellRegistry *shell.Registry
+	notifier      notify.Sender
 }

 func New(cfg config.Config, store storage.Store, logger *slog.Logger) (*Server, error) {
@@ -43,6 +46,7 @@ func New(cfg config.Config, store storage.Store, logger *slog.Logger) (*Server,
 		logger:        logger,
 		connSem:       make(chan struct{}, cfg.SSH.MaxConnections),
 		shellRegistry: registry,
+		notifier:      notify.NewSender(cfg.Notify.Webhooks, logger),
 	}

 	hostKey, err := loadOrGenerateHostKey(cfg.SSH.HostKeyPath)
@@ -159,6 +163,18 @@ func (s *Server) handleSession(channel ssh.Channel, requests <-chan *ssh.Request
 		"session_id", sessionID,
 	)

+	// Send session_started notification.
+	connectedAt := time.Now()
+	sessionInfo := notify.SessionInfo{
+		ID:          sessionID,
+		IP:          ip,
+		Username:    conn.User(),
+		ShellName:   selectedShell.Name(),
+		ConnectedAt: notify.FormatConnectedAt(connectedAt),
+	}
+	s.notifier.Notify(context.Background(), notify.EventSessionStarted, sessionInfo)
+	defer s.notifier.CleanupSession(sessionID)
+
 	// Handle session requests (pty-req, shell, etc.)
 	go func() {
 		for req := range requests {
@@ -194,18 +210,76 @@ func (s *Server) handleSession(channel ssh.Channel, requests <-chan *ssh.Request
 		},
 	}

-	// Wrap channel in RecordingChannel for future byte-level recording.
+	// Wrap channel in RecordingChannel.
 	recorder := shell.NewRecordingChannel(channel)

+	// Set up detection scorer if enabled.
+	var scorer *detection.Scorer
+	var scoreCancel context.CancelFunc
+	if s.cfg.Detection.Enabled {
+		scorer = detection.NewScorer()
+		recorder.WithCallback(func(ts time.Time, direction int, data []byte) {
+			scorer.RecordEvent(ts, direction, data)
+		})
+
+		var scoreCtx context.Context
+		scoreCtx, scoreCancel = context.WithCancel(context.Background())
+		go s.runScoreUpdater(scoreCtx, sessionID, scorer, sessionInfo)
+	}
+
 	if err := selectedShell.Handle(context.Background(), sessCtx, recorder); err != nil {
 		s.logger.Error("shell error", "err", err, "session_id", sessionID)
 	}

-	s.logger.Info("session ended",
-		"remote_addr", conn.RemoteAddr(),
-		"user", conn.User(),
-		"session_id", sessionID,
-	)
+	// Stop score updater and write final score.
+	if scoreCancel != nil {
+		scoreCancel()
+	}
+	if scorer != nil {
+		finalScore := scorer.Score()
+		if err := s.store.UpdateHumanScore(context.Background(), sessionID, finalScore); err != nil {
+			s.logger.Error("failed to write final human score", "err", err, "session_id", sessionID)
+		}
+		s.logger.Info("session ended",
+			"remote_addr", conn.RemoteAddr(),
+			"user", conn.User(),
+			"session_id", sessionID,
+			"human_score", finalScore,
+		)
+	} else {
+		s.logger.Info("session ended",
+			"remote_addr", conn.RemoteAddr(),
+			"user", conn.User(),
+			"session_id", sessionID,
+		)
+	}
+}
+
+// runScoreUpdater periodically computes the human score, writes it to the DB,
+// and triggers a notification if the threshold is crossed.
+func (s *Server) runScoreUpdater(ctx context.Context, sessionID string, scorer *detection.Scorer, sessionInfo notify.SessionInfo) {
+	ticker := time.NewTicker(s.cfg.Detection.UpdateIntervalDuration)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			score := scorer.Score()
+			if err := s.store.UpdateHumanScore(ctx, sessionID, score); err != nil {
+				s.logger.Error("failed to update human score", "err", err, "session_id", sessionID)
+				continue
+			}
+			s.logger.Debug("human score updated", "session_id", sessionID, "score", score)
+
+			if score >= s.cfg.Detection.Threshold {
+				info := sessionInfo
+				info.HumanScore = score
+				s.notifier.Notify(ctx, notify.EventHumanDetected, info)
+			}
+		}
+	}
 }

 func (s *Server) passwordCallback(conn ssh.ConnMetadata, password []byte) (*ssh.Permissions, error) {
--- a/internal/shell/recorder.go
+++ b/internal/shell/recorder.go
@@ -1,12 +1,20 @@
 package shell

-import "io"
+import (
+	"io"
+	"time"
+)

-// RecordingChannel wraps an io.ReadWriteCloser. In Phase 1.4 it is a
-// pass-through; Phase 2.3 will add byte-level keystroke recording here
-// without changing any shell code.
+// EventCallback is called with a copy of data whenever the channel is read or written.
+// direction is 0 for input (client→server) and 1 for output (server→client).
+type EventCallback func(ts time.Time, direction int, data []byte)
+
+// RecordingChannel wraps an io.ReadWriteCloser and optionally invokes a callback
+// on every Read (input) and Write (output). Phase 2.3 will add byte-level
+// keystroke recording here without changing any shell code.
 type RecordingChannel struct {
-	inner io.ReadWriteCloser
+	inner    io.ReadWriteCloser
+	callback EventCallback
 }

 // NewRecordingChannel returns a RecordingChannel wrapping rw.
@@ -14,6 +22,30 @@ func NewRecordingChannel(rw io.ReadWriteCloser) *RecordingChannel {
 	return &RecordingChannel{inner: rw}
 }

-func (r *RecordingChannel) Read(p []byte) (int, error)  { return r.inner.Read(p) }
-func (r *RecordingChannel) Write(p []byte) (int, error) { return r.inner.Write(p) }
-func (r *RecordingChannel) Close() error                { return r.inner.Close() }
+// WithCallback sets the event callback and returns the RecordingChannel for chaining.
+func (r *RecordingChannel) WithCallback(cb EventCallback) *RecordingChannel {
+	r.callback = cb
+	return r
+}
+
+func (r *RecordingChannel) Read(p []byte) (int, error) {
+	n, err := r.inner.Read(p)
+	if n > 0 && r.callback != nil {
+		cp := make([]byte, n)
+		copy(cp, p[:n])
+		r.callback(time.Now(), 0, cp)
+	}
+	return n, err
+}
+
+func (r *RecordingChannel) Write(p []byte) (int, error) {
+	n, err := r.inner.Write(p)
+	if n > 0 && r.callback != nil {
+		cp := make([]byte, n)
+		copy(cp, p[:n])
+		r.callback(time.Now(), 1, cp)
+	}
+	return n, err
+}
+
+func (r *RecordingChannel) Close() error { return r.inner.Close() }
--- a/internal/web/templates.go
+++ b/internal/web/templates.go
@@ -2,6 +2,7 @@ package web

 import (
 	"embed"
+	"fmt"
 	"html/template"
 	"time"
 )
@@ -26,6 +27,18 @@ func loadTemplates() (*template.Template, error) {
 			}
 			return *t
 		},
+		"derefFloat": func(f *float64) float64 {
+			if f == nil {
+				return 0
+			}
+			return *f
+		},
+		"formatScore": func(f *float64) string {
+			if f == nil {
+				return "-"
+			}
+			return fmt.Sprintf("%.0f%%", *f*100)
+		},
 	}

 	return template.New("").Funcs(funcMap).ParseFS(templateFS,
--- a/internal/web/templates/dashboard.html
+++ b/internal/web/templates/dashboard.html
@@ -70,6 +70,7 @@
                <th>IP</th>
                <th>Username</th>
                <th>Shell</th>
+                <th>Score</th>
                <th>Connected</th>
                <th>Disconnected</th>
            </tr>
@@ -81,11 +82,12 @@
                <td>{{.IP}}</td>
                <td>{{.Username}}</td>
                <td>{{.ShellName}}</td>
+                <td>{{if .HumanScore}}{{if gt (derefFloat .HumanScore) 0.6}}<mark>{{formatScore .HumanScore}}</mark>{{else}}{{formatScore .HumanScore}}{{end}}{{else}}-{{end}}</td>
                <td>{{formatTime .ConnectedAt}}</td>
                <td>{{if .DisconnectedAt}}{{formatTime (derefTime .DisconnectedAt)}}{{else}}<mark>active</mark>{{end}}</td>
            </tr>
            {{else}}
-            <tr><td colspan="6">No sessions</td></tr>
+            <tr><td colspan="7">No sessions</td></tr>
            {{end}}
        </tbody>
    </table>
--- a/internal/web/templates/fragments/active_sessions.html
+++ b/internal/web/templates/fragments/active_sessions.html
@@ -6,6 +6,7 @@
            <th>IP</th>
            <th>Username</th>
            <th>Shell</th>
+            <th>Score</th>
            <th>Connected</th>
        </tr>
    </thead>
@@ -16,10 +17,11 @@
            <td>{{.IP}}</td>
            <td>{{.Username}}</td>
            <td>{{.ShellName}}</td>
+            <td>{{if .HumanScore}}{{if gt (derefFloat .HumanScore) 0.6}}<mark>{{formatScore .HumanScore}}</mark>{{else}}{{formatScore .HumanScore}}{{end}}{{else}}-{{end}}</td>
            <td>{{formatTime .ConnectedAt}}</td>
        </tr>
        {{else}}
-        <tr><td colspan="5">No active sessions</td></tr>
+        <tr><td colspan="6">No active sessions</td></tr>
        {{end}}
    </tbody>
 </table>