Fast-growing collaboration tool Slack is bolstering its ranks with new hires from Facebook and Palantir Technologies.

According to a re/code report, Geoff Belknap will be the new chief security officer. He held a similar title at Palantir, a company that builds custom solutions for data analysis.

Keith Adams will be Slack’s chief architect, in charge of building the company's infrastructure.  He comes to Slack from Facebook, where he co-founded the social network’s research into artificial intelligence.

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Along with the new hires, Slack is elevating April Underwood to vice president of product. This also puts her in charge of Slack’s third-party app development fund. The company recently set up the Slack Fund as a way to pump money into startups that want to build apps that integrate into Slack's platform. There are already a number of popular bots and other add-ins, which can be found in Slack's app directory. Top choices include applications and bots like Birdly and Kifi.

Slack describes itself as the “fastest growing B2B application ever” and includes two million daily active users. The company has a number of investors, including Accel Partners, Andreessen Horowitz, The Social + Capital Partnership, KPCB and Google Ventures.