If you've ever used Photo Booth, or any other app using your built-in camera as a source, you may know that there's no way anything less than 1 second is fast enough. There is a very obvious warm-up time in order for the camera to actually warm up and provide an image. Although the problem with timing Photo Booth is that it has to open the app, draw the window, then fire up the camera somewhere in there.
As a matter of testing, I opened up Quicktime Player (Quicktime X) and let it settle down, then I hit File -> New Movie Recording. Luckily for me, the image didn't fire up right away because the built-in camera for my laptop was chosen, but I have the lid closed using an external screen also with a built-in camera.
So I changed the input source to the external camera, and pressed start on my stopwatch as soon as the green LED lit up (which was pretty much immediately). The video started displaying at about 1.5 seconds in. That's still certainly within "blink-and-you'll-miss-it" territory, but only barely.
My answer is that I'm suggesting stray light may be reflecting off of area the LED resides in, invoking an "illuminated" feeling, but that nothing may be happening in reality.
However, I don't suggest that you do nothing. Commercial vendors such as Sophos offer Antivirus products of OS X, Lion-compatible and free too in Sophos' case, and I've also used ClamXAV as a one-off scan-on-demand utility when I've had similar feelings (or when I've wanted to check a file for a windows-using friend, etc.).
Note also that OS X does have built-in spyware protection named, "XProtect", that was born out of the "MacDefender" trojan scare. TUAW has many great articles on the subject under the security tag.
The messages are coming from Spotlight search.
The message themselves are in relation to iPhoto's data on your images. The tags can be found in the AlbumData.xml written out by iPhoto for sharing use (such as Spotlight and other media sharing tools)
Without more information about the version of iPhoto in use, or whether you have any issues with iPhoto itself (and Spotlight's integration) there's not more more I can tell you.
Best Answer
On recent hardware with the T2 chip and new macOS - the camera is controlled in firmware and Apple makes it clear when it's engaged.
Look for a product like MicroSnitch to let you know when recording is happening - whether it's a legitimate program or a covert one.
As long as you are on El Capitan or newer, I have seen zero cases where this isn't a solid detection mechanism.