OpenSSH/WinSCP - Login-"Problem"

[Hellmachine <hellmachine@xxxxxx>]

Dear Mailing List-member,

first of all let me tell you that I am glad to be a member of the list now.

My name is Patrick.

So, and now let's switch to troubleshooting :-)

My environment is a Windows XP SP3 Client running OpenSSH as service. 
SFTP enabled. All works great...a little bit too great :-)

I have the following problem. I have 2 accounts on the SSH: One for me 
and one for my brother.

At work I use putty to connect to my Server. I enabled dynamic 
portforwarding and added localhost and the dynamic port as a Socks-Proxy 
to my browser. Now I can surf the web from anywhere using my 
home-Internet-Connection. That works great.

But even my brother can use this connection...and this is what I do not 
want.

He should be able to connect via SCP-Client (WinSCP) to the SFTP-Server 
but NOT(!) connect via putty and SSH (so he can't use the connection as 
socks-proxy).

But when I diable SSH-connection for his account, even SCP does not work.

Can someone help me? I am a completely newbie to this topic. So, if 
there is a solution, please explain it "slowly and simple"

Thanks in advance

Patrick