Most (77%) of the distributed donuts are based on sub karma. Because this karma can be from voting by any Reddit user, donut distribution remains open to brigading and manipulation. My suggestion to improve defenses against these kinds of attacks is a modification to restrict the set of Reddit users' whose votes count towards the karma used for calculating the donuts distribution. A threshold of earned donuts (1000) would be used to define a user as a "trusted", "qualified", or with some other designation. Votes from this subset of users would count for karma-derived donuts. This designation could be useful for other purposes within the sub, such as less stringent automod rules, saving moderators time when approving content from these users (particularly links in comments).