To anyone who could be interested in security issues:
After analyzing the issue, we realized that there is a static and well known message in response to an ACL Deny from the Sidewinder to the client. As the text of this page (contained in afile within the firewall), is always the same, new versions of nmap (V6.25), has added the fingerprint based in the contents of this file.
Our suggestion for each user is to modify (each case should be different in order for this to be useful), the content of this file with an alternative text other than the standard text given by McAffe.
This suggestion is implemented in some units succesfully and nmap does not recognize anymore he fingerprint.