"It does not matter who it is, heads will roll," Guardiola was quoted in Bild newspaper as having told his players after the game, angry that team tactics had made their way into the press before the game. "I will throw him out. He will not play under me again."
Treble winners Bayern are enjoying a successful first season under the Spaniard.
They have gone four points clear at the top of the Bundesliga and are already through to the Champions League knockout stage, undefeated so far in all three competitions they are taking part.
Saturday's victory was their first against their rivals since 2010 and put them seven points ahead of third-placed Dortmund.
Club CEO Karl-Heinz Rummenigge confirmed the existence of a mole within the Bavarians, saying he should stop or face action from the club.
"We will obviously not bring in the NSA (National Security Agency) to find out who it is," Rummenigge told Sky television. "But I advise him to stop doing it or he will have a serious problem not only with Pep Guardiola but also the entire club."
Bayern, who have already qualified for the Champions League round of 16 with two games to spare, travel to CSKA Moscow on Wednesday.
(Reporting by Karolos Grohmann, editing by Amlan Chakraborty)
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