Flash Player

I work on a Macbook Air. This morning a message appeared inviting me to update "Flash". I have frequently received similar messages in the past and had no reason to doubt authenticity. However, during the process a page appeared looking like the others but inviting me basically to instal MacKeeper - an application which I certainly don't want. I abandoned the instal not knowing if it was genuine or not. I have now re-installed Flash Player which says "Modified and Last opened 17/03/2011". But I play online bridge and am under the impression that Flash is used every time I play. Anyone know what's going on? Thanks.