Google Inc and other companies were investigating on cyber attack by China and more details have emerged.

Adobe Systems, a top maker of design software also said on Wednesday it had suffered a sophisticated and coordinated cyber attack hours later after Google said it may pull out of China.

The ultimate goal of the attack on Google's systems was to access the Gmail accounts of Chinese human rights activists, said David Drummond, Google's chief legal officer.

Google said the attacks took place in mid-December and affected 20 other big corporations.

Two independent, anonymous iDefense sources in the defense contracting and intelligence consulting community confirmed that both the source IPs and drop server of the attack correspond to a single foreign entity consisting either of agents of the Chinese state or proxies thereof, said an iDefense statement.

IDefense, which undertakes intelligence work with many government and Fortune 500 clients, goes on to say that the attack has similar characteristics to an email-based attack in July last year which targeted around 100 Silicon Valley firms.

VeriSign's iDefense managed security services arm has confirmed that state-sponsored parties were to blame.

Considering this proximity, it is possible that the two attacks are one and the same, and that the organizations targeted in the Silicon Valley attacks have been compromised since July, the firm added.

Both companies say that the attacks were unsuccessful.