Free #WiFi@Changi is no longer just a click away.
To access the airport's wireless network with mobile phones and other personal gadgets, travellers now have to pre-register.
The system prompts users for their phone number and sends a message with a password to the handset. Wi-Fi access is activated when the five-digit code is keyed in.
Those without phones can register for a password at the customer service counter.
The Home Affairs Ministry and Changi Airport Group said in a joint reply to The Sunday Times that the "simple authentication process" is part of continuing efforts to further enhance security at the airport.
The aim is to "minimise the risk of exploitation of freely accessible open Wi-Fi networks for malicious purposes", the statement said without elaborating.
Security experts said an open and free Wi-Fi network makes it easier for criminals to communicate with less risk of being traced.
Several airports, including those in Beijing, New Delhi and Munich in Germany, also require users to pre-register for Wi-Fi access.
Others like Kuala Lumpur International Airport and Bangkok's Suvarnabhumi have no such requirement.
Apart from #WiFi@Changi, the Singapore airport also provides more than 500 free Internet kiosks throughout the three terminals for travellers.
In the public areas, visitors can access Wireless@SG - Singapore's wireless broadband programme - which also requires a one-time registration.
The need to beef up airport security has been a focus for many countries since the Sept 11, 2001 terrorist attacks in the United States.
But even as measures are put in place to make flying safer, the authorities have to strike a balance between passenger convenience and the need to ensure security, aviation experts said.
At Changi, the Airport Police work closely with relevant agencies, including Changi Airport Group and the Civil Aviation Authority of Singapore, said commander Sam Tee recently.
"Over-security or under-security is equally sinful and we should not go to the end of each spectrum," he said.
Housewife Annie Lee, 52, said: "The new rule on having to pre-register for Wi-Fi in the restricted area is an inconvenience, of course, but at least it's free. At many airports, you have to pay for Wi-Fi or you are allowed to access the network for a limited time only."