I'm sure I've also read about this, but can't find any links at the moment. The art of Maskirovka [1] (deception and camouflage) is still part of Russian military doctrine. Interestingly, the US also does something similar with planes like the A-10, which has a 'fake cockpit' painted on its underside, so that it is hard to determine the orientation of the aircraft visually. This is actually patented [2] and has been applied to various different aircraft, see the pictures accompanying this answer [3] on stackexchange.
According to wiki the one I was thinking of was the Ka-50
> The single-seat configuration was considered undesirable by NATO. The first two Ka-50 prototypes had false windows painted on them.[19] The "windows" evidently worked, as the first western reports of the aircraft were wildly inaccurate, to the point of some analysts even concluding its primary mission was as an air superiority aircraft for hunting and killing NATO attack helicopters.[20]
> The single-seat configuration was considered undesirable by NATO. The first two Ka-50 prototypes had false windows painted on them.[19] The "windows" evidently worked, as the first western reports of the aircraft were wildly inaccurate, to the point of some analysts even concluding its primary mission was as an air superiority aircraft for hunting and killing NATO attack helicopters.[20]