The US on Thursday called off a military strike against Iran but conducted cyberattacks instead, targeting multiple Iranian computer systems, the New York Times reported.US actions against Iran have reminded us that the boundaries of warfare are being extended. Some American analysts speculate that a war between China and the US can hardly be avoided.If true, online attacks would be a new theater of war to be adopted by the US, and backdoor access to Chinese communications equipment would be its powerful weapon. What Iran is experiencing is a prime example.In 1999, two senior officers in the People's Liberation Army predicted "unrestricted warfare," noting there would be a number of ways to engage an enemy other than direct military confrontation, including cyberattacks, trade wars, new terrorism and ecological warfare. It seems that a US-launched "unrestricted warfare" may already be underway.The US has no lack of a "criminal record" in terms of cyberattacks. Edward Snowden , the US National Security Agency whistleblower, confirmed that Stuxnet, a malware responsible for causing grievous damage to Iran's nuclear program in 2010, was cooperatively developed by the US and Israel. In 2011, it was reported that the US considered using cyber weapons to attack Libya.On June 15, the New York Times reported that the Pentagon has been stepping up its cyberattacks on the Russian power grid. Since at least 2012, the US "has put reconnaissance probes into the control systems of the Russian electric grid," said US officials. Although President Donald Trump strongly denied this claim, it is highly likely that "unrestricted warfare," especially cyber wars provoked by the US, are approaching.Nonetheless, the US has never been ashamed of its record. It has repeatedly hyped in the international community that its cybersecurity is being "threatened," and has targeted China and Chinese companies such as Huawei, alleging there are "hidden backdoors" in Huawei equipment, but has never produced any concrete evidence.This is a groundless label that the US had pinned on China and Chinese enterprises. But who is truly deserving of such label? Anyone with reason will find the answer self-evident.China's National Computer Network Emergency Response Technical Team (CNCERT) released an annual report on June 10, suggesting that most of the cyberattacks targeting Chinese networks in 2018 were conducted by the US.CNCERT found that in 2018, 3.34 million computers on the Chinese mainland were controlled by over 14,000 Trojan or botnet command and control servers in the US, and 3,325 IP addresses in the US planted Trojans in 3,607 websites on the Chinese mainland.We hate to think the worst of the US, but it is the country's own behavior that makes it a concern to the world. Its attacks against multiple countries have revealed its ambitions to control the global network. And its latest cyber war against Iran made it clear what the network controlled by the US looks like.Let's wait and see. US wanton cyberattacks will inevitably be opposed and denounced by the entire international community.