How to detect the original MAC address after it has been spoofed?

Question

We are using the following code for retrieving active MAC address of a windows pc.

private static string macId()
{
    return identifier("Win32_NetworkAdapterConfiguration", "MACAddress", "IPEnabled");
}

private static string identifier(string wmiClass, string wmiProperty, string wmiMustBeTrue)
{
    string result = "";
    System.Management.ManagementClass mc = new System.Management.ManagementClass(wmiClass);
    System.Management.ManagementObjectCollection moc = mc.GetInstances();
    foreach (System.Management.ManagementObject mo in moc)
    {
        if (mo[wmiMustBeTrue].ToString() == "True")
        {
            //Only get the first one
            if (result == "")
            {
                try
                {
                    result = mo[wmiProperty].ToString();
                    break;
                }
                catch
                {
                }
            }
        }
    }
    return result;
}
//Return a hardware identifier
private static string identifier(string wmiClass, string wmiProperty)
{
    string result = "";
    System.Management.ManagementClass mc = new System.Management.ManagementClass(wmiClass);
    System.Management.ManagementObjectCollection moc = mc.GetInstances();
    foreach (System.Management.ManagementObject mo in moc)
    {
        //Only get the first one
        if (result == "")
        {
            try
            {
                result = mo[wmiProperty].ToString();
                break;
            }
            catch
            {
            }
        }
    }
    return result;
}

It works fine to retrieve the MAC address. The problem is when the MAC address is spoofed then it returns the spoofed MAC address. We want to somehow retrieve the original MAC address which is unique and assigned at the factory. Is there any way to do so?

Answer 1

I wish to give an alternative. I don't know if it really answer to 'a way to uniquely identify any computer'.
However, this method query the Win32_BIOS class in System.Management and return a string with high chances to be unique. (Waiting to be disavowed!!)

/// <summary>
/// BIOS IDentifier
/// </summary>
/// <returns></returns>
public static string BIOS_ID()
{
    return    GetFirstIdentifier("Win32_BIOS", "Manufacturer")
            + GetFirstIdentifier("Win32_BIOS", "SMBIOSBIOSVersion")
            + GetFirstIdentifier("Win32_BIOS", "IdentificationCode")
            + GetFirstIdentifier("Win32_BIOS", "SerialNumber")
            + GetFirstIdentifier("Win32_BIOS", "ReleaseDate")
            + GetFirstIdentifier("Win32_BIOS", "Version");
}

/// <summary>
/// ManagementClass used to read the first specific properties
/// </summary>
/// <param name="wmiClass">Object Class to query</param>
/// <param name="wmiProperty">Property to get info</param>
/// <returns></returns>
private static string GetFirstIdentifier(string wmiClass, string wmiProperty)
{
    string result = string.Empty;
    ManagementClass mc = new System.Management.ManagementClass(wmiClass);
    ManagementObjectCollection moc = mc.GetInstances();
    foreach (ManagementObject mo in moc)
    {
        //Only get the first one
        if (string.IsNullOrEmpty(result))
        {
            try
            {
                if (mo[wmiProperty] != null) result = mo[wmiProperty].ToString();
                break;
            }
            catch
            {
            }
        }
    }
    return result.Trim();
}