Just over four months ago, mobile messaging app WhatsApp reported having more than 400 million active monthly users following a successful four-month span that saw 100 million newcomers join the service.

It's essentially déjà vu all over again as the soon-to-be Facebook-owned company has gained another 100 million active users in roughly the same amount of time. At the current rate, WhatsApp is on target to reach the 1 billion user goal that Facebook CEO Mark Zuckerberg is aiming for sooner rather than later.

In a blog post on the matter by co-founder Jan Koum, WhatsApp said they've grown fastest in countries like Brazil, India, Mexico and Russia with users now sharing more than 700 million photos and 100 million videos each day. The executive said they could go on with more numbers but for now, it's more important for them to get back to work.

WhatsApp got started five years ago as a cheaper alternative to SMS text messaging offered by wireless providers. The service gained serious traction over the past year or two, ultimately attracting the attention of Zuckerberg's deep pockets.

In February of this year, Facebook agreed to purchase WhatsApp as part of a deal valued at $19 billion - one of the largest deals in IT history. The Federal Trade Commission approved the acquisition earlier this month but reminded both companies to be mindful of privacy concerns.