apt plugin alert

list Rodolfo Pilas
Sun, 15 Nov 2009 11:03:34 -0200
Message-Id: <user-2a7aa13a5a50@xymon.invalid>

I am receiving an alert about:

Packages not installed from apt repositories:
   linux-image-2.6.18-19-ovz-686

but I wish to ignore this alert because this pakage must be installed.

Can you tell me how to avoid this allert or where to read about it?

Thank you.
Rodolfo Pilas