Arianna Huffington, the famed HuffPost co-founder, says there's one thing that can kill young companies very quickly: Toxic hires.

"I'm allergic to passive aggressive people," Huffington said, on stage at the Inc. and CNBC iCONIC conference in New York City on Wednesday. The event drew hundreds of entrepreneurs and executives to Midtown Manhattan discuss the most pressing challenges that startups face in 2017.

"Going behind someone's back is the way to destroy a company," she added.

Huffington says she puts these principles to practice at Thrive Global, a new startup that she launched last November. Huffington surprised many when she announced in August that she would be leaving HuffPost to focus on the global wellness venture. "Running both companies would have required working around the clock, which would be a betrayal of the very principles of Thrive I've been writing and speaking about," she explained in a statement at the time. Thrive generates revenue primarily by putting on workshops and seminars for clients such as Google, Airbnb and Uber (where she is a board member). It also has a media arm--called the Thrive Journal--where it runs branded content, and it sells some physical products, such as a $100 iPhone bed.

Hiring is one of many areas that Huffington is approaching differently the second time around. For starters, she says, she's quick to recognize passive aggressive managers. "There was a moment [at HuffPost] where I realized that someone who was really good at their job was incredibly toxic," she told the audience. "People came to me complaining about how undermined they were," she added, declining to give the former manager's name. His presence had a negative impact on company morale, she said, and he was subsequently fired.

At Thrive, Huffington has developed a better screening method. "Now during interviews, there is a speech I give to everybody," she said. "I give you full permission to walk into my office and scream at me. But I want you to consider this as my last warning. If you complain about any of your colleagues behind their back," she said, you would be let go. "It does make a difference, because you see how people react."

There's one other thing the media mogul recommends to entrepreneurs: Do not conduct job interviews after a bad night's sleep. "My biggest hiring mistakes were when I was tired and wanted to cross one more thing off of my to do list," Huffington added. "Never interview when you are tired."

After all, your company is a reflection of the men and women you employ. "The biggest mistakes are always hiring mistakes," she said.