Suspected Chinese government-backed hackers have breached computer systems of US law firm Williams & Connolly, which has represented some of America's most powerful politicians, as part of a larger spying campaign against multiple law firms, according to a letter the firm sent clients and a source familiar with the hack....Liu Pengyu, a spokesperson for the embassy, told CNN in response to a separate hacking allegation last month: "China firmly opposes and combats all forms of cyber attacks and cybercrime."