A reputation system generates reputation scores for websites based at least in part on analyses of disposable data misuse associated with the websites. The reputation system receives reports describing disposable data misuses detected by clients and/or other entities, such as credit card issuers. The reputation system also detects certain types of misuse itself by analyzing received disposable data involved in a misuse detection to determine the websites or other entities that misused the data. The reputation system generates misuse statistics describing the amount of data misuse performed by websites. The reputation system generates reputation scores for websites based on the disposable data misuse statistics and, optionally, other reputation information for the websites, such as malware distribution associated with the websites. The reputation system reports the reputations of the websites to the clients.