Espionage Strategy

Is there anyone out there that can provide some good espionage strategy?

I'm particularly interested in defense strategy.  I'm playing two games right now where my money is being taken.  It's not reported in the Daily European (so I don't know what province the spy is in) and I really only noticed because my cash reserves are low as it is.

I have tried placing 4 information spies in 4 of my oponents (so 4 per country) who I think are doing this.  I got one report that showed me country 1 defense spies and another showing country 2 espionage spies.  Should I up the info spies?  Place a bunch of defense spies in a province and rotate hoping to find the location?

Any additional strategies in general you all use is always welcome as well.

Normally your defense spies will provide the information on the whereabouts of the enemies espionage spies. This will then allow you to place spies in that province. I also find that the more defensive spies i have in general the more of theirs get captured, when using espionage i normally place my spies on their harbors. This will hinder their resource production and prevent battleship production. Also use your info spies to see where they are producing offensive weapons, mostly r.guns, bombers, ships etc as they have a long production timescale, then stack several espionage spies in those provinces to damage and delay production. The more spies you stack the better the chance of severe damage.