LEADING THE DAY: The Secret Service will investigate after hackers left a Twitter message saying President Obama had been assassinated on a Fox News Twitter account, the Washington Post reported. On Monday, hackers broke into the account, saying the Obama had been shot by an unknown gunman in Iowa.

Hackers had a busy weekend, with members of the AntiSec hacker collective posting what is believed to be usernames and passwords from an unimportant Apple server, CNET reported.

Vice President Biden joins Twitter:In the run-up to the 2012 election, Vice President Biden has joined Twitter, using the handle @VP. According to the White House blog, Biden’s staff will keep the feed updated with announcements as well as “a behind the scenes look at Veep-life.”

President Obama recently started sending his own messages from his Twitter account, and will participate in Twitter town hall this Wednesday.

Microsoft, Baidu enter agreement: Microsoft and Baidu have signed a deal for Bing to handle some of the Chinese search giant’s English-language search results, the Associated Press reported. Google and the Chinese government have had a tense relationship; Google has about 19.2 percent of the search market in China.

Cisco, HP, consider Chinese surveillance project: Wall Street Journal reported that Cisco is among a handful of Western companies involved in the early stages of constructing a surveillance network in China. The system, to be built in the southwest city Chongqing, will cover an area more than 25 percent larger than New York City.

Citing “people familiar with the matter,” the report says that Cisco is expected to supply networking equipment for the project, though a Cisco spokesman told the Journal that it “hasn’t sold video cameras or video-surveillance solutions in any of our public infrastructure projects in China.” The report mentions that Hewlett-Packard and Alabama software company Intergraph might also bid on the project.

Sandberg’s role at Facebook: Facebook COO Sheryl Sandberg, known not only for her role at the company but also for her much-buzzed TED talk on female executives, was profiled in the New Yorker for its upcoming issue. The article outlines Sandberg’s career — including stops at Harvard, the Treasury Department and Google — and highlights the unique way she’s carved a place for herself in the male-dominated Silicon Valley environment.

The profile also reveals some of what Facebook is thinking about Google +, privacy and its “inevitable” IPO.