The latest cyberattacks from China mark the first known case in which Google has seen its defences penetrated so comprehensively, forcing the world's biggest internet company on to the back foot in an attempt to limit the damage.

Google confirmed yesterday its security had failed to keep out attacks aimed at its main infrastructure, which had led both to the theft of some of the company's own intellectual property as well as details of two Gmail accounts.

These attacks were more serious than other related infiltration attempts made by planting malicious software, also known as malware, on users' computers or by tricking them to gain access – the methods most commonly used by cybercriminals and spies.

Alma Whitten, a security engineer at Google who was involved in the company's investigation, said Google's systems had succumbed to direct attack that exposed the two different types of data, but added the company was confident it could tackle the problems.

“Security is always going to be an ongoing process,” she said. “We have the resources at Google to have a very large security team with wide expertise – we can bring all of that to bear.”

Ms Whitten said the attempts to hack into Google's systems had been “very customised attacks” aimed both at the company itself as well as the PCs of some of its users. This makes them more sophisticated than the usual assaults mounted by hackers as they search for a way into a company's systems.

She also said Google was confident it had traced the source of the attacks back to China, though she would not reveal further details.

In response, the company said it began rolling out an extra layer of security to all users of is Gmail system on Tuesday night. It has offered Gmail users the option of using secure hypertext transfer protocol secure (HTTPS) connections since 2008, but had left it optional because that can slow the speed at which e-mails are transmitted. But on Tuesday it made this the default option for all users.

Meanwhile, some industry observers questioned the link between Google's decision to end censorship and the security breaches.

“The logical connection between being hacked by attackers appearing to originate from China and therefore rethinking their policy on censorship is not as crisp as one might hope for,” said Whit Andrews, an analyst at Gartner, an information technology research company. “The decision to pull out of China will not stop Gmail accounts being [attacked] or people trying to get hold of Google's intellectual property. They seem to be using these incidents as a casus belli.”