how to spoof MAC address via code

I got curious so I pulled the source for MadMACs. Turned out to be pretty straightforward to port the core logic to C#, so here it is if anyone is interested.

private const string baseReg =
    @"SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\";

public static bool SetMAC(string nicid, string newmac)
{
    bool ret = false;
    using (RegistryKey bkey = GetBaseKey())
    using (RegistryKey key = bkey.OpenSubKey(baseReg + nicid))
    {
        if (key != null)
        {
            key.SetValue("NetworkAddress", newmac, RegistryValueKind.String);

            ManagementObjectSearcher mos = new ManagementObjectSearcher(
                new SelectQuery("SELECT * FROM Win32_NetworkAdapter WHERE Index = " + nicid));

            foreach (ManagementObject o in mos.Get().OfType<ManagementObject>())
            {
                o.InvokeMethod("Disable", null);
                o.InvokeMethod("Enable", null);
                ret = true;
            }
        }
    }

    return ret;
}

public static IEnumerable<string> GetNicIds()
{
    using (RegistryKey bkey = GetBaseKey())
    using (RegistryKey key = bkey.OpenSubKey(baseReg))
    {
        if (key != null)
        {
            foreach (string name in key.GetSubKeyNames().Where(n => n != "Properties"))
            {
                using (RegistryKey sub = key.OpenSubKey(name))
                {
                    if (sub != null)
                    {
                        object busType = sub.GetValue("BusType");
                        string busStr = busType != null ? busType.ToString() : string.Empty;
                        if (busStr != string.Empty)
                        {
                            yield return name;
                        }
                    }
                }
            }
        }
    }
}

public static RegistryKey GetBaseKey()
{
    return RegistryKey.OpenBaseKey(
        RegistryHive.LocalMachine,
        InternalCheckIsWow64() ? RegistryView.Registry64 : RegistryView.Registry32);
}

For brevity’s sake, I’ve left out the implementation of InternalCheckIsWow64(), but that can be found here. Without this, I was running into issues with not finding the registry I wanted due to structural differences between 32- and 64-bit OSes.

Obligatory disclaimer — play with the registry at your own peril.