Less than a month after the United States and China signed an agreement to prevent economic espionage from being conducted online, a cloud security company has said that China is continuing to attempt to breach US companies.

"Over the last three weeks, CrowdStrike Falcon platform has detected and prevented a number of intrusions into our customers' systems from actors we have affiliated with the Chinese government," Crowdstrike co-founder and CTO Dmitri Alperovitch said in a blog post.

"The very first intrusion conducted by China-affiliated actors after the joint Xi-Obama announcement at the White House took place the very next day -- Saturday, September 26. We detected and stopped the actors, so no exfiltration of customer data actually took place, but the very fact that these attempts occurred highlights the need to remain vigilant despite the newly minted cyber agreement."

Alperovitch said that hacking attempts continue to persistently occur, with SQL injection being the preferred attack vector used.

Last month, US president Barack Obama said that "cyberthreats" to American companies and citizens have to stop.

"The United States government does not engage in cyber economic espionage for commercial gain. And today, I can announce that our two countries have reached a common understanding on the way forward ... So this is progress. But I have to insist that our work is not yet done," he said.

A fact sheet released by the White House said the US and China would make an effort to promote "appropriate norms of state behavior in cyberspace".

"The United States and China agree that neither country's government will conduct or knowingly support cyber-enabled theft of intellectual property, including trade secrets or other confidential business information, with the intent of providing competitive advantages to companies or commercial sectors," the White House said.

Alperovitch said that a delay between the signing of the agreement and its implementation was expected.

"We need to know the parameters for success, and whether the parties to the agreement discussed a time frame for implementation or, instead, expected it to be immediate," he said.

"I personally remain encouraged by the administration's efforts to reduce the number and scope of Chinese intrusions and to have China draw a public distinction between national security-related espionage, which virtually every advanced nation engages in, and espionage done for commercial benefit, which the US government and industry believe is unacceptable and must stop."