The Yahoo Inc. accounts of at least three journalists and an analyst became inaccessible over the last few weeks. They were greeted with messages saying, "We've detected an issue with your account" and were told to contact Yahoo, they said Tuesday. Yahoo technicians told one of the four that his account had been hacked and restored his access, but it was not clear if the other instances were related.
Sensitivity about Internet security has run high since Google Inc. announced in January it might leave China after a series of cyberattacks and complaints about censorship. Last week, Google made a partial retreat, shutting down its mainland-based search engine and redirecting those queries offshore, to the freer Chinese territory of Hong Kong.
Analysts have been watching closely to see if China retaliates for Google's high-profile departure from the mainland search engine market.
Many redirected queries appeared blocked Tuesday on the Hong Kong-based search engine. Although searches for benign terms were met with results on Chinese competitors such as Baidu.com and Soso.com, an error page would pop up when the same terms were typed into Google.com.hk.
Google initially blamed the trouble on an internal revision that inserted some coding that the company thought had caused China's automated censors to block material that normally wouldn't be prohibited.
But Google backed off its original explanation within a few hours.
After further investigation, the company said it realized the changes in its search settings had occurred a week ago without disrupting its results in mainland China. That discovery led Google to conclude the trouble stemmed from changes in China's "Great Firewall" - the nickname for the tools the government uses to block access to sites deemed to be subversive or pornographic.
Without doing anything on its end, Google said its search traffic from mainland China appeared to be flowing freely again early Wednesday morning in Beijing.
"We will continue to monitor what is going on, but for the time being this issue seems to be resolved," Google said.
Web searches weren't the only Google service bogging down in China. The company reported that access to its mobile services in the country were "partially blocked" this week after experiencing no issues last week. Google didn't provide a reason for the mobile disruption.
It was not clear where problems with the Yahoo e-mail accounts originated. All four people affected are professionally focused on China and related issues. They said they had heard of other colleagues having similar problems, including one journalist who lost his Yahoo account entirely in January.
Clifford Coonan, China correspondent for The Independent and the Irish Times newspapers, said he received the "issue with your account" notice when he logged in Tuesday. Another reporter said she received repeated error messages from Yahoo last month.
The Western analyst said he was locked out of his account for four or five days, until he spoke with a Yahoo representative Monday who went through the security questions and restarted it.
"He said somebody had hacked into my registration details," said the analyst, who would not give his name, citing the sensitivity of the issue. The analyst said he was concerned hackers may have also accessed his inbox.
Yahoo, based in Sunnyvale, California, issued a statement Tuesday condemning all hacking attacks and vowing to "take appropriate action in the event of any kind of breach."
Coonan wondered whether he was just part of a broad attack against Yahoo's e-mail accounts, or if he had been specifically targeted.
"I'd just be interested to see if anyone in the business community or outside of journalism and academia has had the same problem, then it might be less sinister," he said. "It's obviously annoying but if it's just journalists and academics, that's scary."