Hi, madhazelnut. The rule was changed a while ago. The chance for successful infiltration is determined by comparing the levels of espionage and counter-espionage and the number of sent and defensive spies of the spying and spied player, respectively. The espionage works with a formula which gives equal chances for success when the technologies’ levels and number of spies are equal. Could you tell me where exactly did read
According to help articles, if the counter espionage level is 5 or more than the espionage, the spies should not succeed infiltrating.