From its clients, Mandiant identifies four industries as receiving the bulk of attacks: aerospace and defense, 31 percent; energy, oil and gas, 17 percent; pharmaceuticals, 15 percent; and finance, 11 percent.
Mandiant identified one unit of China's People's Liberation Army that allegedly has hacked 141 companies and organizations since 2006, removing "technology blueprints, propriety manufacturing processes, test results, business plans."
What's unclear is how "infrastructure" systems (electricity grids and the like) have been penetrated and, on command, might be compromised.
In the mid-1980s, most such systems were self-contained. They relied on dedicated phone lines and private communications networks. They were hard to infiltrate.
Since then, many systems switched to the Internet. "It's cheaper," says James Andrew Lewis, an Internet expert at the Center for Strategic and International Studies.
The architects of these conversions apparently underestimated the risk of sabotage.
As yet, there is little. One publicized incident occurred in 2012 when hostile software ("malware") infected an estimated 30,000 computers of Aramco, Saudi Arabia's oil company. Business operations suffered, but oil production and delivery continued.
More powerful was the Stuxnet virus, reportedly developed by the United States and Israel to disrupt Iran's nuclear program.
The future could be more tumultuous.
If the United States attacked Iran's nuclear facilities, Lewis thinks it would retaliate with cyberattacks against banks and electricity networks. Press stories report that Iran has already increased its attacks.
There's a race between cyber offense and defense.
All this qualifies our view of the Internet.
Granted, it's relentless. New uses spread rapidly. Already, 56 percent of U.S. adults own smartphones and 34 percent have tablets, says the Pew Internet & American Life Project.
But the Internet's social impact is shallow.
Imagine life without it. Would the loss of email, Facebook or Wikipedia inflict fundamental change?
Now imagine life without some earlier breakthroughs: electricity, cars, antibiotics. Life would be radically different.
The Internet's virtues are overstated, its vices understated.
It's a mixed blessing - and the mix may be moving against us.