Economic Undermining
Targeting the opposition through reduction of Credit Advantage. Because resources are often very causally connected to various units and structures this can deal a lot of undoing. In its most basic and easy for it is accomplished by destroying enemy resource gatherers. However destroying the resource boxes themselves can be effective. Also spending resources with a builder infected with nanites is an option that doesn't cause "unit attacked" messages.
When such economic disturbance is done early enough the undoing of the act might act as further economic undermining (for example the player no longer affording to build more resource processors). It can also be targeted against different types of resources.
A player that doesn't use every resource available to him will have a buffer to protect against economic undermining. If an act of economic undermining is undone the boost in resources carries over to the future.