The world’s two biggest credit card transaction processors, Visa and MasterCard, are exploring ways to profit from consumer information and open up new opportunities to advertisers.

By selling access to the data about what people spend, the transaction companies may provide an important first link between offline spending and online advertising opportunities. Although they are both at the exploratory phases of these information-sharing plans, the fact that they are being considered is making advertisers – and privacy advocates – take notice.

Linking ads to consumer behavior. Currently, online advertisements are linked directly to browsing behavior. Visa and MasterCard’s plans would offer advertisers the ability to display ads based on purchases that are made offline. For example, if a person uses a Visa card to buy fast food, that same person may be shown weight loss advertising later on when they browse online.

MasterCard and Visa do not issue credit cards, but rather handle the processing of transactions made with those cards. The transactions are relatively anonymous. Both companies collect the date, time, dollar value, merchant name and other spending behaviors – but the name and address of the cardholder do not appear. Visa processed 45 billion transactions in the year ending September 2010 and MasterCard processed approximately 23 billion.

MasterCard proposed an idea to ad executives that would sell the purchased attributes paired with names and addresses provided by a third-party company. The proposal was shared with at least four companies, but has been put aside for the time being. They are currently exploring a plan to sell the use of the anonymous aggregated data sorted into marketing segments.

However, MasterCard is now proposing a plan to sell marketers an analysis of anonymous, aggregated data sorted into marketing segments – people likely to be interested in international travel. Visa is pitching ability to use anonymous buying histories.

Both companies note that their plans are very preliminary, but they still raise many questions about anonymity from privacy advocates and other watchdog groups.