The massive Equifax Inc. data breach has triggered demands onCapitol Hill for stiffer rules and new requirements for whatfinancial companies must do to fend off cyberattacks.

Yet tougher oversight would all but certainly require supportfrom the Trump administration and buy-in from congressionalRepublicans—both groups that want to reduce financial regulation,not stiffen it. Democrats so far have led the calls for more rulesin the wake of Equifax's disclosure that 143 million Americans'personal information was stolen.

Tighter constraints would pose a particularly difficult choicefor GOP lawmakers because it would most likely mean furtherempowering the Consumer Financial Protection Bureau, acontroversial agency created after the 2008 financial crisis thatmany Republicans have been trying to weaken or put out of businessalmost from its first day of existence. No other federal regulatorsupervises Equifax or has officials inside the firm conductingon-site exams.