"There is rich data already available but it's locked away in NGO offices and there's no way to search across data to understand the trends and make connections," said Xinyi Duan, technical director for Hong Kong-registered Liberty Asia.

Duan is working with local charity Helpers for Domestic Helpers to collect complaints that domestic helpers have made in the past and to create an intake system for new cases.

"It's very common for agencies to charge fees of up to HK$21,000, which is much more than the maximum amount of 10 per cent of the worker's first month's wages that Hong Kong agencies are allowed to charge. That's a lot of money for workers," said Holly Allan, manager of Helpers for Domestic Helpers.

From 2011 to 2013, the charity received 12,000 complaints from helpers of which more than half were about illegal agency fees. Last year only six employment agencies were convicted of violations, according to the Labour and Welfare Bureau.

Allan said employers suffered too.

"Some agencies are in collusion with moneylenders to get helpers to take out loans to pay off the fees, and then the moneylenders harass not only workers but employers as well if workers fail to pay," she said.

An employer from Tsuen Wan told the her family had been harassed for the past three months over a debt of HK$30,000 that her helper was unable to repay.

"We received 100 calls from the loan shark each day. We had to change our phone numbers and the locks on our doors and we still live in fear, and police have refused to open a case," Mrs Chan said, refusing to give her full name.

Central and Western district councillor Joseph Chan Ho-lim said many domestic helpers used their Hong Kong household address for loan applications, so the employers at that address were usually disturbed when their maids failed to repay their loans.

"Some employers simply choose to pay the money to avoid the disturbance," he said.

Since recent helper-abuse allegations have come to light in Hong Kong, such as the case of injured Indonesian maid Erwiana Sulistyaningsih, more attention has been paid to the excessive fees charged by employment agencies.

Agencies in Hong Kong and agencies in helpers' home countries often worked together to make sure fees were repaid and agencies can hide illegal fees by using moneylenders as intermediaries, according to Puja Kapai, director of HKU's Centre for Comparative and Public Law.

Even though anyone can file a complaint against moneylenders, whose licences must be renewed every year, Allan said it could be difficult to process enough information to file reports because the forms the charities and NGOs collected from helpers were kept as hard copies and not digitised.

Personal information, such as names of helpers, would be scrubbed from the database to avoid compromising victims' identities, said Duan. Helpers would have to sign a consent form before their data was used.

Liberty Asia won the Global Impact Award from Google last year to use technology to fight human trafficking in Asia. The prize came with top-of-the line data-entry software from Salesforce, a cloud computing company, and analysis tools from Palantir, an American company that has provided software to global intelligence agencies.

The group will also work to collect data on sex and labour trafficking activities in Southeast Asia.

Kapai said she would work with pro bono lawyers to help bring a few test cases to court.

"In previous court cases I've observed, judges did not believe the testimony of helpers. Because agencies and moneylenders have legitimate businesses and are working with cash payments, it is hard to trace cases of overcharging. That's why we require a lot of data gathering to identify a clear pattern of exploitation," she said.

Human rights lawyer Robert Tibbo said the information would be useful in court only if the data was of high quality.

"If there's poor data, it doesn't matter how good a storage system you have. But if the quality and scope of the data is high quality, it would be fantastic to have it used in court," he said.

Lawyer Robert Connelly, who specialises in migrant worker issues, expressed scepticism.

"This project could be a valuable advocacy tool, but the problem in Hong Kong is that there is a lack of political will to make changes to legislation, such as abolishing the two-week rule, that would effectively protect helpers," he said, referring to the rule requiring helpers to leave Hong Kong within two weeks of terminating a contract.

"Hundreds of complaints have been filed [against] agencies but the government has failed to bring a reasonable number of prosecutions."

Labour and welfare secretary Matthew Cheung Kin-chung said last month that he believed penalties for unscrupulous employment agencies were "too low".