Hackers may have targeted more banks than have been previously reported, according to prepared remarks by the chief executive officer of Swift, the global interbank messaging system is set to give on Tuesday.

The Society for Worldwide Interbank Financial Telecommunication will increase security requirements for the software clients use and help clients conduct security audits, the network's chief executive officer, Gottfried Leibbrandt, will tell an audience at the European Financial Services Conference in Brussels, according to prepared remarks of the speech, which is slated to be delivered today. 

Leibbrandt's speech comes after hackers exploited weaknesses in how banks connect to the network to steal $81 million from Bangladesh's central bank in February and $12 million from an Ecuadorean bank in January 2015. An attack late last year on a Vietnamese lender was foiled.