Beijing branded a new U.S. spending bill barring government purchases of Chinese-made technology "biased" on Thursday, after the two powers clashed over accusations of cyber-hacking.

The bill, signed Tuesday by President Barack Obama, blocked government buying of information technology equipment "produced, manufactured or assembled" by firms "owned, directed or subsidised by the People's Republic of China".

The United States is deliberately sparring with al-Qaida supporters and militants online aiming to shoot down extremist messages and win over hearts and minds, a U.S. official said Wednesday.

Seeking out the virtual spaces where "al-Qaida and its supporters lurk" is part of America's strategy to combat violent extremism, Under Secretary for Public Diplomacy and Public Affairs Tara Sonenshine told students at the University of Maryland.

A "bazooka" cyber attack described as the most powerful ever seen has slowed traffic on the Internet, security experts said Wednesday, raising fresh concerns over online security.

The attacks targeted Spamhaus, a Geneva-based volunteer group that publishes spam blacklists used by networks to filter out unwanted email, and led to cyberspace congestion that may have affected the Internet overall, according to Matthew Prince of the U.S. security firm CloudFlare.

Google on Thursday began offering the chance for people to wander virtually through an abandoned town deep within the exclusion zone around Japan's crippled nuclear plant.

Visitors to the Internet giant's mapping site can take a tour through the overgrown and deserted streets of Namie, where time appears to have stood still for two years.

Twitter is on pace to earn more than a half-billion dollars in ad revenue this year and close to $1 billion next year, industry tracker eMarketer estimated on Wednesday.

About 53 percent of the ad revenue at Twitter this year will come from use of the service on smartphones or tablets in a huge jump from 2011, when the San Francisco company took in no money from mobile ads, according to eMarketer.

Apple appeared in a Shanghai court on Wednesday, accused by a Chinese firm of copying software used for the "Siri" personal assistant on its hugely popular iPhones.

The Californian company's products are big sellers in China, and chief executive Tim Cook said in January he expects it to surpass the U.S. as the firm's largest market, but the relationship is sometimes troubled.

A new edition of the dystopian "BioShock" shooter videogame released Tuesday puts Americanism in the crosshairs, taking on taboo topics including slavery and racism.

The "BioShock Infinite" protagonist battles a cult devoted to US founding fathers in a fictional floating city of Columbia that clings to early 1900s Americana and shuns the notion of an Emancipation Proclamation.

Facebook chief Mark Zuckerberg is helping form a group to lobby for U.S. political reform in areas such as education and immigration policy, according to U.S. media reports spreading online Tuesday.

The San Francisco Chronicle, Politico, and the Wall Street Journal were among outlets reporting that the 28-year-old co-founder of the world's leading social network was helping unite technology industry in a political action group.

Google has picked 8,000 people in the U.S. who will have a chance to wear the company's new Internet-connected glasses, which are being described as the next breakthrough in mobile computing.

Google Inc. began notifying contest winners Tuesday.

T-Mobile USA on Tuesday said it will start offering the iPhone 5 on April 12, filling what its CEO said was "a huge void" in its phone lineup.

T-Mobile, the fourth-largest of the national U.S. phone companies, has been losing customers to the bigger companies, which all sell the iPhone.