If you live in China, don't even think of using the Internet to read up on Tiananmen Square or surf for porn. But if you want to take a shot at hacking into American military computer systems, there may be a place for you in the Chinese military. Reports are spreading that US government sources are confirming their beliefs that the Chinese military has "hacked" into Pentagon computer systems, including one that serves the office of Defense Secretary Robert Gates.

The story first appeared at the Financial Times, where an unidentified source is quoted as saying that there was a "very high level of confidence... trending towards total certainty" that the attacks were the responsibility of the People's Liberation Army. Although it doesn't appear that sensitive data was compromised, the report is troubling because it shows China can strike at even high-level military systems and even knock some offline (some Pentagon computers were off-network for a week after the attack).

Of course, the article rightly notes that the US itself is engaged in an international game of probing military networks around the globe, so this could be a tit-for-tat attempt at hacking. With secure networks now providing battlefield intelligence, live feeds from drone aircraft, and communications channels for much of the military, network warfare and defense are becoming increasingly crucial.

The threats don't always come from governments, either. Entire nations can have web services disrupted by criminals utilizing vast botnets to choke off access to government agencies or web sites. In fact, this appears to have happened to Estonia earlier this year when a massive DDoS attack kept several state sites down for multiple days. Suspicion in the Estonia attack focused quickly on Russia, with some NATO officials worried enough about the situation to journey to Estonia in order to "observe" the attack firsthand.

But botnet attacks, by their very nature, can be almost impossible to trace back to the controller. In the case of Estonia, the country's prime minister eventually blamed the matter on "criminal activity" rather than official Russian government involvement. Could the Chinese attack turn out to have a similar origin?

To be sure, just because you can trace something to China doesn't mean that the Chinese government or military is involved. In fact, a new report from Sophos released today says that 49 percent of malware sites in August of this year were hosted somewhere in China.

Whatever the cause, such events do encourage organizations to take much closer looks at their computer and network security practices. The Pentagon has already announced that it will conduct a comprehensive audit of its systems in order to tighten them up further.

We have contacted the Defense Department's media office for further comment.

Update:

China denies the report that it was involved in the hacking. A foreign ministry spokesperson told the BBC that "some people are making wild accusations against China... These are totally groundless and also reflect a Cold War mentality."