domain security problem

[Hegedus Gabor]

hi,

my configuration: 
radius 2.X , win 2003 AD,  domain: TEST,  802.1x

I have a problem:

If the pc is in the domain(TEST) it can authenticate good.
If it is not in domain it can't auth, it is good, BUT when i set the 
computer name to TEST and it is not in the domain(simple workgroup) it 
CAN authenticate.
I use ntml_auth for the authentigation.
    ntlm_auth = "/usr/bin/ntlm_auth
        --request-nt-key --domain=%{mschap:NT-Domain}
        --username=%{mschap:User-Name}
        --challenge=%{mschap:Challenge:-00}
        --nt-response=%{mschap:NT-Response:-00}"


How can I fix this risk?
What are the solutions?