stop users access internet thru proxy

Dear all,

I have a problem regarding ISA 2000. In my W2k network I have ISA as the proxy and I had applied an access policy which will allow only those users who had been given permission on ISA using their W2K login/account’s password. The problem is that users are sharing their passwords with other people who are not given internet access formally. This is eating up my bandwith and as a result the accesss of internet is not fast.

Kindly suggest me a way to block more than one instanceof accessing internet using single uesrname & password. By this only one person will be able to access internet with the authorised username and password. Hope you got my problem.

Your help is highly appreciable and as an act of kindness I will be thankful to you for your help.

Regards,

Abdul Aziz