In a blog post, Mr Koum sought to reassure users that Facebook’s $19bn (£11bn) purchase of the firm would not change core principles.
“Respect for your privacy is coded into our DNA,” he wrote.
The post comes in the wake of complaints to US regulators by privacy advocates about Facebook’s purchase.
Mr Koum referenced his childhood in Ukraine in the 1980s, and wrote that “the fact that we couldn’t speak freely without the fear that our communications would be monitored by KGB is in part why we moved to the United States when I was a teenager”.
He said he would not have allowed the firm to be acquired by Facebook if it meant changing core WhatsApp policies like not asking for users’ names, email addresses or birthdays. He said he would not allow user data to be used for advertising.
“Speculation to the contrary isn’t just baseless and unfounded, it’s irresponsible,” he added.
“It has the effect of scaring people into thinking we’re suddenly collecting all kinds of new data. That’s just not true.”
WhatsApp currently makes money by selling a $0.99 subscription to users.
Mr Koum previously railed against advertising in a 2012 blog post.
But privacy advocates have asked US regulators to block the purchase, arguing that Facebook has a long history of promising not to use user data for advertising purposes, only to do just that.
In a filing with the Federal Trade Commission, two privacy groups – the Electronic Privacy Information Center and the Center for Digital Democracy – argued that WhatsApp users provided the firm with personal data under the assumption it would not be shared.
“Users provided detailed personal information to the company including private text to close friends. Facebook routinely makes use of user information for advertising purposes and has made clear that it intends to incorporate the data of WhatsApp users into the user profiling business model,” wrote the groups.
“The proposed acquisition will therefore violate WhatsApp users’ understanding of their exposure to online advertising and constitutes an unfair and deceptive trade practice, subject to investigation by the Federal Trade Commission.”
The FTC has not yet said whether it will open an investigation.