"thieves from *** causing trouble within our lands!"

Is there any way to see exactly what they're doing? "Causing trouble" doesn't say anything except that I've been targeted.

Or is that message just to let me know someone did a "spy on", "survey" etc. operation?

it means thieves were caught but their source is unknown, for any op.

if you have shadowlight cast and receive an intel op, you will get a message to the effect of "xxx (y:y) was responsible for this attack"

that message tells you someone attempted something but failed, as far as i know it doesn't matter what op they used, be it sabotage, intel or an attempt to steal you will always get that same message if the opponent fails his attempt. Sometimes you also get the addition of the perpetrator added at the end, but i'm not sure how that particular part works, if its just a set chance to discover who was behind the op or if some other variables come into play.

I use shadowlight but even without it it's telling me who did it. Right now I have six of those messages, two of them with shadowlight but the others tell me anyway.

So it means this person has been trying and failing?

shadowlight only works on the first op done on you after casting it.

All those other msgs are people that have been trying to op you and failing