dirty tricks

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun plural Covert intelligence operations designed to disrupt the economy or upset the political situation in another country.
• noun plural Unethical behavior, especially acts undertaken to destroy the credibility or reputation of an opponent.
• noun plural Commercial espionage.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun underhand commercial or political behavior designed to discredit an opponent