Apparently China isn’t too pleased about recent allegations that its military is behind a spate of cyber attacks on US corporations, infrastructure and media organizations over the last couple of years. Following up from the usual angry denials of responsibility, China went one step further yesterday, accusing US officials of orchestrating similar hacking attacks against its own infrastructure.

During a press briefing yesterday, China’s Ministry of Defense once again reiterated the supposed shortcomings of a report by security firm Mandiant accusing it of carrying it cyberattacks on the US. That report was “factually inaccurate and unprofessional”, it said, stressing that hacking is illegal under Chinese law.

The agency then went on to describe that it too had found evidence of a “growing number of cyberattacks” against its own websites and those of the China’s military, many of which seem to have originated in the US. An investigation into attacks on two specific military sites revealed that 62.9% of them came from US IP addresses, the Ministry added.

Given this evidence, observers might conclude that China has every right to be angry at the US, but the fact that it cites IP addresses as ‘evidence’ of US involvement is contradictory to say the least. Following the Mandiant report, Defense Ministry spokesperson Geng Yansheng was quick to point out that experienced hackers can easily steal IP addresses, hence they cannot be considered as proof of responsibility for an attack.

“Everyone knows that the use of usurped IP addresses to carry out hacking attacks happens on an almost daily basis,” Yansheng said in an interview with Reuters.

To be fair to China, there probably is some truth to its allegations – I’d be more than willing to bet that the US has carried out some infiltrations to at least test the defences of China’s computer networks, even if it hasn’t actually been engaged in any cyber-spying.

But irrespective of whether or not China’s ‘evidence’ is credible, the accusations serve to illustrate how cyber attacks are quickly becoming a major irritant to relations between the two countries. The US has long suspected China of being the main actor behind cyber attacks on US computer networks, but it’s only in recent years that officials have started being more vocal and making such accusations in public.

Tit-for-tat attacks on each other’s government and military systems are one thing, but its China’s corporate hacking that’s really irked the US. China has never presented evidence of, nor accused the US of hacking into its company’s systems, and in all likelihood it probably doesn’t happen too often, whereas with the Chinese the practice is endemic.

It might be due to this that China has actually been quite restrained in its own criticism of the US. The Defense Ministry refrained from specifically accusing the US of attacking it, instead just alluding to that fact. Nonetheless, it did cite recent reports in US media that claim that the US policy allows President Obama to launch “pre-emptive cyber attacks” as evidience of American aggression against it.

“Such practices are not conducive to the joint efforts of the international community to enhance internet security. We hope that the US will explain and clarify this policy,” read the statement.