[X4U] Application Folder - Permissions for unknown user.

[John Erdman]

Sorry about this repost. For some reason my first attempt didn't seem  
to go thru... but some did receive it.

I recently looked at the info on my Applications folder. I noticed  
that besides Myself (Read & Write Access) and Everyone (No Access)  
there are two "users" listed as "(unknown)". The user icons are grayed  
out. The first has Read & Write permissions. The second is listed as  
Read Only.

Even when I access the Sharing & Permissions to make changes, I am  
unable to change either of the unknown's permission levels.

There are no unknown users listed in System Preferences>Accounts.  
Guest accounts are disabled. So far I've been unable to discover the  
source.

I don't like having unknown entities having write access to my  
computer. I suspect these "unknown" users might be related to an Adobe  
or Apple updater but I don't know for sure. I'd at least like to know  
if this is a normal state of affairs or if I ought to be more concerned.

Should I be concerned?
Who are the Unknown Users?
How can I find out who/what they are?
How can/Should I remove them?

TIA,

John

OS 10.5.5, 24" iMac 2.16 GHz Intel
Not on a network.
Have broadband internet access via phone line DSL. Behind a NAT router.
I am the only user of this computer.
Also, I am fairly cautious about what I download or give permissions to.