The video below demonstrates how Google and the rest have been, according to most news reports, exploited via the “Aurora” vulnerability in Internet Explorer, and had their “intellectual property” taken.
In the video you will see Metasploit set up a listening session, set up a web site that serves up the malicious code, and watch as an unsuspecting user visits the web site, triggers the attack that uses the IE vulnerability, and unknowingly opens a connection to a computer owned by the attacker. The attacker then lists the user’s processes, and elects to kill Notepad where the user was working on an important document. IE 6.0 is used, as this is the version Microsoft references as having been used in the “targeted attacks” on some 30+ U.S. companies.
A silly example for demonstration to be sure, but once the backdoor is open to the user’s PC the attacker can use it as a pivot point for other attacks against the internal network, escalate his or her privileges, take information off the PC, basically do anything the user can do.
Here the attack vector (click to make it bigger):