Phillip Lahm does not want a ring of steel thrown around the German training facilities despite revealing there was a spy in their camp.
Team news was leaked to the press just hours ahead of their 4-2 demolition of Greece on Friday.
The inclusion of Miloslav Klose, Andreas Schurrle and Marco Reus ahead of Mario Gomez, Thomas Muller and Lucas Podolski was meant to give the German team the element of surprise over the 2004 champions.
But boss Joachim Low was shocked to see his team selection being reported by a news agency just an hour after his lunchtime announcement to the squad.
Skipper Lahm revealed they are only allowed to tell their immediate family members of their inclusion after football chiefs believe the mole to be an agent representing one of the squad rather than a player betraying his team-mates.
"It is an issue, I must admit it and I think now everyone should be aware who he passes the line-up to," Lahm said. "We must be extra careful now.
"Whether someone plays or they do not play, it is out of the question to pass the line-up to advisors. Exchanges with closest family are understandable, but that is it.
"It's a pity if leaks occur. The whole nation is behind us so it's a disgrace for the line-up to be in the public eye so early.
"The one with the problem is the guy who has done this because he is damaging the hopes of the entire nation. It's a shame, but we won't be hiring a detective."
Hoffenheim coach Markus Babbel believes the mole could damage Germany's chances of being crowned kings of Europe and told Sport1 that the leaks are "frustrating, unnecessary and stupid".
"We all have the goal of becoming European champions,"said Babbel. "If there is somebody there spreading things like this, then he is not doing German football any favours.
"At the end of the day, we all suffer because of it."
Low is sweating on the fitness of star midfielder Sebastian Schweinsteiger ahead of their semi-final showdown with Italy in Warsaw on Friday.
Lahm admits that while the loss of his Bayern Munich team-mate would be a blow the German squad proved they have plenty of strength in depth already this tournament.
"We have 23 top category players and the coach is spoilt for choice," Lahm added. "The strength of our squad was visible in the last two matches.
"We are content with four wins in a row and being in another semi-final but the objective is to win in the Ukraine next Sunday."