fix: resolve recent service scan regressions

plugins/services/vnc_test.go

@@ -3,10 +3,59 @@
 package services
 
 import (
+	"context"
 	"errors"
+	"net"
+	"strconv"
+	"sync/atomic"
 	"testing"
+	"time"
+
+	"github.com/shadow1ng/fscan/common"
 )
 
+func TestVNCDisableBruteOnlyChecksUnauthenticatedAccess(t *testing.T) {
+	listener, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer listener.Close()
+
+	var connections atomic.Int32
+	go func() {
+		for {
+			conn, err := listener.Accept()
+			if err != nil {
+				return
+			}
+			connections.Add(1)
+			_ = conn.Close()
+		}
+	}()
+
+	host, portText, err := net.SplitHostPort(listener.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+	port, err := strconv.Atoi(portText)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cfg := common.NewConfig()
+	cfg.DisableBrute = true
+	session := common.NewScanSession(cfg, common.NewState(), &common.FlagVars{})
+	result := NewVNCPlugin().Scan(context.Background(), &common.HostInfo{Host: host, Port: port}, session)
+	if result == nil || !result.Success || result.Service != "vnc" {
+		t.Fatalf("Scan() = %#v, want identified VNC service", result)
+	}
+
+	time.Sleep(20 * time.Millisecond)
+	if got := connections.Load(); got != 1 {
+		t.Fatalf("connections = %d, want one unauthenticated-access check and no password attempts", got)
+	}
+}
+
 func TestClassifyVNCErrorType(t *testing.T) {
 	tests := []struct {
 		name string