Phorm is conducting the largest trial of its controversial online advert-targeting technology with its first customer outside the UK.
The deal with South Korean broadband provider KT will give Phorm with the opportunity to prove its technology on one of the world's most advanced networks, according to the Financial Times.
Korea has 15 million broadband subscribers, and Phorm estimates that the online advertising market is worth £1.1bn a year.
Opposition from privacy groups has delayed full UK implementation of the Phorm technology, which helps advertisers target web users based on their browsing habits.
Only a limited trial with 10,000 BT customers has been conducted in the UK. Virgin Media and Carphone Warehouse have also signed deals with Phorm, but no trials have been announced.
Privacy campaigners have sent an open letter to leading web companies demanding they resist the introduction of the Phorm tracking system by BT, Virgin and TalkTalk.
The future of behavioural targeting technologies like Phorm's is uncertain in Europe, where officials could rule that consumer profiling by advertisers breaches privacy laws.
In the UK, opponents of the Phorm technology maintain that it is illegal under the Regulation of Investigatory Powers Act.
Earlier this month, Baroness Miller of Chilthorne Domer, Liberal Democrat home affairs spokeswoman, asked the government to delay the roll out of Phorm technology until its legality had been established.