Reportedly, the four had conducted "systematic searches" for employees' materials, shared it beyond their jobs despite warnings and even set notifications for what people were doing and when, including medical appointments. This led to targeted staffers feeling "scared or unsafe," Google said. Calendar screenshots and other details reportedly found their way to people outside Google.

Rivers hasn't commented beyond her tweet confirming the firing. Google has acknowledged the memo but declined to say more.

Whatever happened, the firings are unlikely to ease high tensions between Google and its rank-and-file staff. Protesters at Google's San Francisco campus on November 23rd accused the company of using the alleged security violations (as a pretext for cracking down on organizing workers and placing them on indefinite leave. While it's not clear if the protesters were aware of the extent of the allegations at the time, this won't likely assuage their concerns that Google is retaliating against employees who speak out -- not when the firm has scaled back town meetings, hired an anti-union consultancy and dealt with past complaints about retaliation.