If you are not the direct employee of that organisation for whom you are hiring then you can mention industry or organisation level
For Example:- Telecom Industry, Big 4 organisation etc.
You should not mention the client name it should be confidential once a person will contact to you at that time you can disclose the client name.
6th December 2017 From India, Delhi
There is no hard and fine rule for it, but yes you need to have an approval from your client to go forward with it. As if your contract with the client has any of such clause or your client does not with to put his name on the add or post then better not to do. Also, if client is OK to put his name then you can go ahead with it. Thus please consult with your client before taking further decision.
6th December 2017