Makes your private or protected serialized fields non editable from Unity editor

ReadOnlySerializeFieldAttribute.cs

using System;
using UnityEngine;
using System.Collections;

[AttributeUsage(AttributeTargets.Field)]
public class ReadOnlySerializeFieldAttribute : PropertyAttribute
{
    public ReadOnlySerializeFieldAttribute()
    { }
}
#if UNITY_EDITOR
using UnityEditor;
[CustomPropertyDrawer(typeof(ReadOnlySerializeFieldAttribute))]
public class ReadOnlySerializeFieldDrawer : PropertyDrawer
{
    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        var value = GetPropertyValue(property);
        var propertyName = property.displayName;

        EditorGUI.LabelField(position, string.Format("{0}: {1}", propertyName, value), EditorStyles.boldLabel);
    }

    public static object GetPropertyValue(SerializedProperty prop)
    {
        if (prop == null)
            throw new System.ArgumentNullException("prop");

        switch (prop.propertyType)
        {
            case SerializedPropertyType.Integer:
                return prop.intValue;
            case SerializedPropertyType.Boolean:
                return prop.boolValue;
            case SerializedPropertyType.Float:
                return prop.floatValue;
            case SerializedPropertyType.String:
                return prop.stringValue;
            case SerializedPropertyType.Color:
                return prop.colorValue;
            case SerializedPropertyType.ObjectReference:
                return prop.objectReferenceValue;
            case SerializedPropertyType.LayerMask:
                return (LayerMask)prop.intValue;
            case SerializedPropertyType.Enum:
                return prop.enumValueIndex;
            case SerializedPropertyType.Vector2:
                return prop.vector2Value;
            case SerializedPropertyType.Vector3:
                return prop.vector3Value;
            case SerializedPropertyType.Vector4:
                return prop.vector4Value;
            case SerializedPropertyType.Rect:
                return prop.rectValue;
            case SerializedPropertyType.ArraySize:
                return prop.arraySize;
            case SerializedPropertyType.Character:
                return (char)prop.intValue;
            case SerializedPropertyType.AnimationCurve:
                return prop.animationCurveValue;
            case SerializedPropertyType.Bounds:
                return prop.boundsValue;
            default:
                return "Can not handle this types.";
        }
    }
}
#endif