The spies and the counter-espionage

[Handel]

The game hints says "Keep some spies in the borders of your empire for counter-espionage"
But I made experiments and found out only the spies which are on the same tile as your spy actually reduce the chance of success. And the reducing is only 15% per a counter-espionage spy.
So keeping spies for counter-espionage is useless. Except maybe if you have a single extra-super-duper resourse and must keep it at all cost. So something like 6-7 spies exactly on the tile will practically eliminate the enemy spies.
As for the towns and such - the best the AI could manage was to poison the water and 1-2 times destroyed the accumulated hammers for an unsignificant buildings. Not a single try to destroy a wonder or anything big.

Edit: Ooops - please move this to BTS forum

 

[Kesshi]

Handel,

I find the most annoying thing abount spies is when they pillage a Town down to a Village. Now I'm losing 3 commerce and 1 hammer (before modifiers) per turn! And there are jus too many Towns to keep Spies watching over all of them, so I'm bound to lose a few.

 

[Bushface]

I greatly doubt that multiple spies will help protect a resource, as even one spy (or a security bureau) protects a city just as well as a dozen. Beyond that, all you can do is to run counter-espionage missions every 10 turns, which doubles all the enemy's espionage mission costs, and try to get lots more EPs against him than he has against you.
However, enemy spies can always get through. I had a factory destroyed despite having a SecBu in the city, a recent counter-esp mission, and about a 4:1 EP ratio over the villain - the latter went up to over 6:1 because of his high mission cost.

 

[Magma_Dragoon]

If a city has nothing else to build, I'll make a few spies and put one in each city. I'm pretty sure spies also increase the chance of catching idle enemy spies, so spies waiting for the -50% EP cost bonus have a high chance of being caught before those 5 turns are up.

 

[Kesshi]

Magma_Dragoon,

When does that ever happen?

 

[Magma_Dragoon]

If I have a low production city with no more commerce multipliers left to build.

 

[Handel]

The AI uses its spies randomly and stupidly. Sometimes it destroys a bronze mine (at the time when no one needs the bronze anymore), sometimes it destroys a random farm; 1 harbor, 1 walls (when they were obsolete) and once sabotaged the hammers for a temple... It likes to poison the water which is practically useless...
All the destructions are at small and unsignificant cities because I guess it has not enough EP to try and sabotage something important in a big city.
In my last game I have a single tile with an ivory. No spy ever targeted it.
Edit: And I have 2 gems mines right at the border. Again no one ver tried to sabotage either of both.