Google says it is tightening the security of its free email service to combat hackers like the ones that recently targeted it in China.
With the shift, Gmail accounts will automatically be set in a "https" mode, meaning the contents of emails will be scrambled so they are less likely to leak out to unauthorised users.
Previously, only the log-in data was encrypted.
Google had not been using this more secure format as Gmail's default setting because it could be slower than the unprotected mode.
The shift to the more secure setting began on Wednesday (New Zealand time), just a few hours after Google announced Chinese hackers had pried into the email accounts of human rights activists.
Google was now considering pulling out of China and shutting down its search engine there because of the attacks, the company said in an online statement.
Internet security company AVG (Australia/NZ) Pty yesterday said the FBI had warned cyber attacks were potentially more dangerous than a nuclear attack and weapons of mass destruction.
AVG marketing manager Lloyd Borrett said that with PCs now containing up to 200 million lines of code, of which two million could include bugs, and with homes full of mobile phones, games consoles and PDAs, the potential for falling prey to hackers and identity theft was a real and growing threat.
"We expect our workplace computers and data to be protected to the highest level, but people are failing to fully protect their personal information. With cyber criminals becoming ever more sophisticated, it is crucial to be protected at home."
Each line of code in a computer could include bugs that were easily infiltrated by hackers.
A virus in a computer might only be an inconvenience, but identity theft was a real concern, he said.
Meanwhile, Yahoo Inc said it supported rival Google's threatened departure from China because of computer attacks that pried into the email accounts of human rights activists.
In a statement yesterday, Yahoo said it was "aligned" with Google's reaction to the hacking that originated within China.
Google has promised to stop censoring its search results in China, defying the country's Government.
The move may result in Google pulling out of China completely.
Yahoo, based in Sunnyvale, closed its offices in China in 2005, when it sold its business there to the Alibaba Group.
As part of that deal, Yahoo retained a 39% stake in Alibaba, which represented one of Yahoo's most valuable assets.
Yahoo spokeswoman Nina Blackwell declined to say whether its solidarity with Google would cause the company to sell its Alibaba holdings, AP reported.
Before selling its Chinese business, Yahoo's co-operation with the Chinese Government angered human rights activists and United States lawmakers.
Much of the scathing criticism focused on Yahoo's role in the jailing of two Chinese journalists.
The evidence against them included emails Yahoo turned over to the Chinese Government.
In 2007, Yahoo settled a US lawsuit filed on behalf of the Chinese journalists.
Shortly before the case was settled, a US lawmaker denounced the company's executives as moral "pygmies" during a Congressional hearing.
