North Korea's Internet and 3G networks were back to normal by midday Tuesday after hours of a strange shutdown. This blackout led to speculation that North Korea had been under cyber-attack from the US. It remains unknown whether the purported US-North Korea conflict will flare up into full-blown cyber war.

Sony Pictures, which has caught global attention for filming The Interview, a movie featuring the fictional assassination of North Korean leader Kim Jong-un, was attacked by a group of hackers recently. The FBI asserted that these hackers were sponsored by North Korea, and US President Barack Obama declared the US would make a "proportional response." Thus, there are high suspicions that Washington is behind the attack.

Neither Washington nor Pyongyang has commented officially on the incident. There are more threats to cyber security than ever before, and hacking groups not backed by governments have become mainstream. Countries like the US have established cyber armies, but there has been no declaration of a cyber war so far. Any party suspected of launching cyber invasions using its regular cyber army always denies its involvement.

We hope that Washington and Pyongyang will not engage in war in cyberspace. Once they cross the Rubicon, there is no way back.

The current suspected tit-for-tat situation between North Korea and the US raises the risks of a cyber war. Pyongyang has shown its abomination toward Sony Pictures. However, having denied any connections with the attacks, it hailed these actions as justified.

Washington has revealed its inclination to retaliate against Pyongyang, which is why many assume the Internet blackout in North Korea was its doing. Washington's response could be an overreaction, as it is implying that cyber attacks can be seen as a kind of legitimate state action, which will set a precedent for cyber wars.

Antagonism between North Korea and the US will remain a hot topic for quite a while in the international community. If more cyber attacks are launched in the near future, many people will believe that a cyber war between them has already broken out.

It is possible that Washington is trying to teach Pyongyang a lesson and show its strength through cyber attacks. But it must keep in mind that its advanced networks also have loopholes, which might be taken advantage of by a single hacker and a computer.

The US must not set an example by engaging in cyber warfare. It might prevail in the short term, but the already vulnerable Internet order will be mired in countless trouble.

This North Korea-US cyber conflict has also reminded China that it must reinforce its cyber security and act as a constructive role to guard peace across the Internet. As for the speculation that it was China that cut off North Korea's Internet connections, these are spurious and do not merit our attention.