How to audit object grants to PUBLIC

I can't get my 8.1.6 db to audit basic object priv grants if the grantor owns the object. EX. foo says:

grant select on foo.bar to public;

It doesn't show up in dba_audit_trail.

Can anyone tell me how to audit such actions? I've already combed through sql reference, dba guide, concepts, metalink, etc etc. Auditting ALL by <owner> doesn't do it, auditting GRANT TABLE by <owner> doesn't do it. What does? Does anything?

TIA.
CS Received on Thu May 09 2002 - 16:49:17 CDT