Logging on to my Yahoo email account this week, I was greeted with the message: "We've detected an issue with your account." My inquiries appeared to reveal that this was part of a sophisticated and co-ordinated hacking campaign against journalists, academics and rights activists based in China, or dealing with the China story elsewhere.
The attacks seem to be focused solely on Yahoo email accounts. It is not clear who is behind the hacking, but sensitivities about internet security have been high since the web giant Google started to fulfil its January promise to pull out of China in response to cyber attacks on rights activists and censorship.
But the attacks occurred not just in China. Around a dozen journalists and analysts, based in cities including Washington DC, Taipei and Beijing, have been affected by the cyber-attacks, and all of them are involved in reporting on or analysing China in some way. One journalist received a similar message to mine, referring to an "issue" with his account, and spent nearly a day trying to get things sorted out with Yahoo.
Another reporter had a similar problem two months earlier, and while at the time it seemed innocuous, it now looks as if it was part of a similar campaign. A US reporter, engaged in a sensitive book project about Tibet, lost his Yahoo account entirely for three weeks.
My suspicions were heightened when I saw that United States had been spelt "Unites States" in the second reference of the message on the Yahoo page that came up when I tried to access my email account. Bad spelling is a classic sign of email scams or efforts to install malicious software (malware) on a computer; often it is the only way you can tell that you are the subject of a scam.
One analyst said that Yahoo had told him that somebody was trying to get hold of his registration information, and that his account had been frozen until they could clear up what happened. The attacks show the growing sophistication of computer hackers and the difficulty that web companies have in protecting accounts.
Beijing denies any involvement in attempts to hack into rights activists' email accounts. However, a report this week by the computer security firm Symantec named Shaoxing, a winemaking city in the Zhejiang province of China, as the world's malware capital.
Symantec's MessageLabs Intelligence Report for March 2010 said that nearly 30 per cent of targeted malware attacks came from China, with 21.3 per cent coming from Shaoxing alone. Next was Taipei with 16.5 per cent, followed by London with 14.8 per cent.
Accredited foreign journalists have freedom to move around China to report and are never censored. However, journalists also have to get used to working within certain research restrictions in China.
The system of internet controls known as the Great Firewall of China, limits the methods available for basic research as it blocks anything the government does not want you to see, including the long-banned YouTube, Facebook and Twitter.
It has been a bad week for China's reputation as a place to do business. After a short trial four executives from the mining giant Rio Tinto were given hefty jail sentences for corruption and stealing secrets. They confessed to taking bribes and were sacked by Rio Tinto, but the court process was not transparent and was partially closed to reporters.
Two weeks ago, Google said it would stop censoring internet search results in China, a move that was hailed by rights groups but that angered the Chinese authorities.
Last week, Google began its slow retreat from the mainland Chinese market, redirecting its search engine to Hong Kong. Google's decision to quit has caused widespread anger in China, and difficulties have arisen when logging on to Google.com.hk; these appear to be related to changes introduced in the mainland. Some wags have said that China could end up as the world's largest Local Area Network (LAN) as its system of tough controls leads to it becoming isolated from the global online community.
The shape of Yahoo's business in China has always been very different from Google's. In 2004, Yahoo turned over private email data to the Chinese government that was subsequently used to prosecute the journalist Shi Tao, who was jailed for 10 years.
Yahoo responded with the establishment of a human-rights fund to provide legal aid to victims of government censorship. In 2005, Yahoo sold its China business to Chinese online group Alibaba, although it retained a 39 per cent stake in Alibaba.
Yahoo said it condemned all cyber attacks regardless of origin or purpose, but it did not go into specifics.