Mandiant's report is available online; here are some of their conclusions:

The nature of “Unit 61398’s” work is considered by China to be a state secret; however, we believe it engages in harmful “Computer Network Operations.”
» Unit 61398 is partially situated on Datong Road (大同路) in Gaoqiaozhen (高桥镇), which is located in the Pudong New Area (浦东新区) of Shanghai (上海). The central building in this compound is a 130,663 square foot facility that is 12 stories high and was built in early 2007.
» We estimate that Unit 61398 is staffed by hundreds, and perhaps thousands of people based on the size of Unit 61398’s physical infrastructure.
» China Telecom provided special fiber optic communications infrastructure for the unit in the name of national defense.
» Unit 61398 requires its personnel to be trained in computer security and computer network operations and also requires its personnel to be proficient in the English language.

APt1 has systematically stolen hundreds of terabytes of data from at least 141 organizations, and has demonstrated the capability and intent to steal from dozens of organizations simultaneously.

» Since 2006, Mandiant has observed APT1 compromise 141 companies spanning 20 major industries.aPt1 has systematically stolen hundreds of terabytes of data from at least 141 organizations, and has demonstrated the capability and intent to steal from dozens of organizations simultaneously.
» Since 2006, Mandiant has observed APT1 compromise 141 companies spanning 20 major industries.
» APT1 has a well-defined attack methodology, honed over years and designed to steal large volumes of valuable intellectual property.
» Once APT1 has established access, they periodically revisit the victim’s network over several months or years and steal broad categories of intellectual property, including technology blueprints, proprietary manufacturing processes, test results, business plans, pricing documents, partnership agreements, and emails and contact lists from victim organizations’ leadership.
» APT1 uses some tools and techniques that we have not yet observed being used by other groups including two utilities designed to steal email — GETMAIL and MAPIGET.
» APT1 maintained access to victim networks for an average of 356 days. The longest time period APT1 maintained access to a victim’s network was 1,764 days, or four years and ten months.
» Among other large-scale thefts of intellectual property, we have observed APT1 stealing 6.5 terabytes of compressed data from a single organization over a ten-month time period.
» In the first month of 2011, APT1 successfully compromised at least 17 new victims operating in 10 different industries.
» APT1 has a well-defined attack methodology, honed over years and designed to steal large volumes of valuable intellectual property.aPt1 has systematically stolen hundreds of terabytes of data from at least 141 organizations, and has demonstrated the capability and intent to steal from dozens of organizations simultaneously.
» Since 2006, Mandiant has observed APT1 compromise 141 companies spanning 20 major industries.
» APT1 has a well-defined attack methodology, honed over years and designed to steal large volumes of valuable intellectual property.
» Once APT1 has established access, they periodically revisit the victim’s network over several months or years and steal broad categories of intellectual property, including technology blueprints, proprietary manufacturing processes, test results, business plans, pricing documents, partnership agreements, and emails and contact lists from victim organizations’ leadership.

Fans of sf author William Gibson recall that the Chinese intrusion programs were the best technology you could get:

`What is this thing?' he asked the Hosaka. `Parcel for me.'
`Data transfer from Bockris Systems GmbH, Frankfurt, advises, under coded transmission, that content of shipment is Kuang Grade Mark Eleven penetration program. Bockris further advises that interface with Ono-Sendai Cyberspace 7 is entirely compatible and yields optimal penetration capabilities, particularly with regard to existing military systems...'

He slotted the Chinese virus, paused, then drove it home.
`Okay,' he said, `we're on..."
`Christ on a crutch,' the Flatline said, `take a look at this.'
The Chinese virus was unfolding around them. Polychrome shadow, countless translucent layers shifting and recombining. Protean, enormous, it towered above them, blotting out the void.
`Big mother,' the Flatline said.
(Read more about Gibson's Kuang Grade Mark Eleven Penetration Program)