Something odd happened a few weeks ago. A Hong Kong internet surfer using Yahoo as his search engine started to notice that certain searches no longer returned results. A closer examination of the screen revealed that his search engine had switched on its SafeSearch facility. Eager to continue his quest for evidence that Paris Hilton does, sometimes, disrobe, he clicked the SafeSearch button to switch it off and discovered that it was no longer possible to do so. Quietly and with no explanation, Yahoo has shut the door to anyone using certain parts of its search engine to access anything it classifies as adult content. 'We did not find results for 'sex',' users hoping to find salacious images are being informed. The same goes for 'porn', 'adult' or indeed any word that might produce an image that Yahoo considers obscene. Except for 'obscene', oddly enough. That still returns a mixed bag of images, including a woman in a bra, Robert Mugabe and an amusingly shaped carrot. It is not only Hong Kong that is affected. Singapore, South Korea and India have also found the door to one of the internet's most popular subject areas shut to their local IP addresses - some more firmly than others. At least in India there appears to be a reason: a change in the country's Information Technology Act (based on the 150-year-old Section 292 of the Indian Penal Code), which bans publication of pornographic material, has meant the authorities are now able to take action against a wide range of providers, from internet search engines and ISPs to cyber cafes. But why pick on Hong Kong? True, there exists the Control of Obscene and Indecent Articles Ordinance but that has been in place since 1987 and there has hardly been a clamour from the authorities for it to be used to shut down large parts of the internet. If Yahoo has a reason, it is keeping it to itself. Asked why Hong Kong had been selected for special treatment, the company says only that when it introduced territory-specific versions of its services, it did so 'keeping user safety and trust a top priority'. In a statement, it said: 'Yahoo's policies in these markets reflect our commitment to comply with the law while protecting our users' rights to freedom of expression and privacy. To further these commitments, Yahoo has had SafeSearch filters, designed to limit certain adult or sexual content, activated in specific markets for a number of years. We continue to review local guidelines and our own policies to ensure we are meeting our obligations under the law and to our users.' Flickr, the photograph-hosting website owned by Yahoo, suggests Hong Kong is populated by sensitive souls in need of special protection. 'Flickr is a global community made up of many different kinds of people. What's OK in your back yard may not be OK in theirs. Each one of us bears the responsibility of categorising our own content within this landscape. So, we've introduced some filters to help everyone try to get along. 'Note: If your Yahoo ID is based in Hong Kong, Singapore, India or Korea, you will only be able to view safe content based on your local terms of service [meaning you won't be able to turn SafeSearch off].' The filters - which appear to differ in range from place to place - are hardly comprehensive; searches for text results in Hong Kong still return an eyewatering list of pornographic websites on a par with a search made in the most liberal of jurisdictions. Images, however, are filtered fairly strictly and video more so. It is not just Yahoo that is suffering from a bout of squeamishness. Microsoft has also introduced a net nanny, for Hong Kong users of its Bing search engine, launched last summer. Anyone using Bing to search for anything the internet giant deems to be unwholesome has found that instead of an interesting and edifying set of results, they are being greeted with the message: 'Your country or region requires a strict Bing SafeSearch setting, which filters out results that might return adult content.' A company spokeswoman says that, in general, it allows users to set their own limits on what they might find on the Net but there are some exceptions: 'By default, in most markets, all searches are set to moderate, which restricts visually explicit search results but does not restrict explicit text. 'Bing categorises certain countries as strict markets, such as Hong Kong. In these strict markets, we might restrict the display of adult content (as locally defined) and because of the local customs, norms and laws, we might limit SafeSearch settings only to 'strict'. Set to 'strict', SafeSearch filters the display of explicit search results in images, videos and text.' Bing does offer a 'Go to Bing in the United States' link that circumvents restrictions but why does Microsoft feel the need to tiptoe around Hong Kong as if it were dealing with the mainland? Google - which censors its search results in the mainland - has no such qualms in Hong Kong; its search engine here will still happily cater for whatever depths of depravity its users care to plumb. What appears to have happened is that lawyers for Yahoo and Microsoft have been flicking through the local legislation - possibly on the internet, since both Bing and Yahoo seem to have no objection to returning text and images for the search term 'indecent' - and have decided to err on the side of caution. The Control of Obscene and Indecent Articles Ordinance (Cap 390) makes it an offence to publish an obscene article. That includes placing something on a website, which carries a penalty of up to three years imprisonment and a fine of up to HK$1 million. In 2007, a Hong Kong man was prosecuted under the act and fined HK$5,000 (he pleaded guilty and had an otherwise clean record) for posting a message with an internet link to an overseas porn site. A year later, in the most high-profile case, a 24-year-old computer technician admitted distributing over the Web obscene images of pop star Edison Chen Koon-hei and a number of young women involved in the entertainment industry. Even then, the prosecution was criticised by some human-rights groups. In contrast, the mainland arrested more than 5,000 people for internet porn offences last year and closed down 9,000 websites for carrying pornographic content. Hong Kong-based social media expert Thomas Crampton thinks the companies are making a mistake. 'It is disappointing to see a company restricting access to the internet at any level,' he says, pointing out that there appears to be no legal requirement for the filters. 'It is not characteristic of Hong Kong.'