virtuous-action subterfuge
Refers to a seemingly-beneficial/praiseworthy action that you perform in order to cover up a past/present transgression.
Three classic examples of a virtuous-action subterfuge would be:
(1) Pretending to be cleaning up litter along a roadside, in a park, or in some other public area, and then disposing of your bags of collected trash in a nearby dumpster; in reality, of course, you merely picked up just a very few pieces of discarded trash during periods when others were looking --- the bags of trash you're carrying are mostly YOUR OWN household garbage that you're disposing of for free in someone else's dumpster, rather than paying for your own trash-disposal.
(2) Pretending to be helpfully delivering bags of groceries to a tenant of a "wrinkle city" apartment-complex; as in Example #1, however, those bulging shopping-bags are merely still-new-looking shopping-sacks that you've carefully saved from previous grocery-shopping trips and then filled with your own trash; your confederate apartment-tenant later quietly disposes of said bags in the complex's waste-bin along with his own garbage.
(3) Pretending to be cleaning/dusting a certain area of a room, whereas in reality you are covering up the fact that you either have meddled with something you weren't supposed to touch, or currently wish to do so. By cleaning the entire area that the “off-limits” object is occupying, it would seem natural for you to move/handle the object itself in the course of your cleaning, and so no observers will think twice about your harmlessly displacing the item "just to clean around/underneath it".