The C.I.A. developed tools to spy on Mac computers by injecting software into the chips that control the computers' fundamental operations, according to the latest cache of classified government documents published on Thursday by WikiLeaks. All of the surveillance tools that have been disclosed were designed to be installed on individual phones or computers. But the effects could be much wider. Cisco Systems, for example, warned customers this week that many of its popular routers, the backbone of computer networks, could be hacked using the C.I.A.'s techniques. Julian Assange, the founder of WikiLeaks, has offered to share the precise software code used by the C.I.A.'s cyberweapons with the affected companies. But major tech companies have been reluctant to directly engage with him for fear of violating American laws. The spy software described in the latest documents was designed to be injected into a Mac's firmware, a type of software preloaded in the computer's chips. It would then act as a "listening post," broadcasting the user's activities to the C.I.A. whenever the machine was connected to the internet. Tools that operate at the chip level can hide their existence and avoid being wiped out by routine software updates. Under an agreement struck during the Obama administration, intelligence agencies were supposed to share their knowledge of most security vulnerabilities with tech companies. The C.I.A. documents suggest that some key vulnerabilities were kept secret.