On the day that they entered the headquarters of a renowned technology company, the security unit was nondescript—quiet as a mouse. It had to be that way, naturally.

For months prior, the tech behemoth’s upper management had suspected that something nefarious was going on inside their organization: files were disappearing; millions of dollars’ worth of intellectual property was being copied, they believed; personal and private information, too. Worse, the executives in the corporate suite were mystified about their culprit.

But they recognized the veracity of an adage in the tech industry: there are two kinds of companies—those that have been hacked, and the ones that haven’t been hacked yet. As the tech company’s workers endeavored on their quotidian tasks that day, perusing their computers, carrying on with their familiar series of tasks, the security sleuths surreptitiously flipped open their laptops, connected to the network, and subtly began their forensics investigation.

The team ran software to search for viruses and malware, which turned up nothing. They checked the servers for illicit software, which similarly turned up an absence of leads.

Eventually, the operatives from the security company set up network-monitoring tools to detect where traffic might be leaving the building. Soon enough, their screens were filled with charts and numbers—reds, yellows, greens—that zigzagged up and down like an E.K.G. Read more from vanityfair.com…

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