The security  model doesn't allow for that. I'm also not aware of any 3rd party
add-ons that allow it.

Sorry. I am sure there must be a way. I think i did not explain my question
correctly. There we go....

How can we give security  to a web  part (say "group listing")?

Say I have a "group listing" webpart  and I want all users  to access  it to add it
to their web pages.

Right now the users can see some webparts and some they can't. I want to give
them access to see some and some not. Say I want them to add "group listing
webpart" to their pages and don't want them to see "Area Detailed webpart"

All those web parts I have are SPS delivered webparts.

No, you explained things correctly. What you are asking is not possible - there
is no way to set security  on individual web  parts in the web part  galleries.

Is it possible to entire web  part gallary???????

The only available security  related to web  parts is whether a user  can add a web
part (either from a gallery or via upload) to the current page. There is no
security on the galleries.

As stated there is no gallery or Web Part security. The only way to
"hide" the existence of a Web Part in the gallery ( and by that I mean
the Web Part definition) is to not have it in the gallery. This is an
all or nothing proposition. You could remove the Web Part from the
gallery and make it available for import by exporting and saving the
definition file to a secured place such as Team Site document library.
Users would then need to do an import and not a browse to add the Web
Part.