Can technology help combat the modern slavery business?
Growing up in rural Cambodia, Khai Socheung knew that life was tough, and that she might have to leave her homeland to find work.
So, when she was offered a job in China paying up to $1,000 (£590) a month - more than she could earn at home - she decided to go.
It would help her family pay off their debts, and she thought, would be "a good opportunity for me to leave the country for a better life".
It did not turn out that way.
Socheung had fallen victim to a Chinese and Cambodian gang of people traffickers. When she arrived, instead of giving her a job, the gang sold her to a man for $15,000.
"On the first night he tried me to force me to sleep with him but I refused, then he turned angry. He just raped me repeatedly every night," she says.
Determined to escape, Socheung persuaded the gang's leader to buy her a Sim card, saying she needed it to keep in contact with her family.
Eventually she managed to get in contact with Licadho, a human rights charity based in Phnom Penh, which helped her get repatriated to Cambodia.
Socheung says she refused to give up: "I was so angry at them for tricking me, but I could not do anything.
"I needed to control myself until I was able to contact the NGO [non-governmental organisation]."
Her story is not uncommon and the trafficking of poor Cambodian women into China is on the increase, says Pung Chiv Kek of Licadho.
"If you don't punish everybody, especially the officials, then they will continue. It's good business."
According to the International Labour Organization, there are 21 million modern slaves across the globe - trafficked and working as forced labourers.
Slavery in all its forms is tough to beat partly because it crosses so many borders and involves organisations which do not always work together effectively.
If a woman is reported missing in one country, and is then recorded as a prostitute in another, her plight will not automatically be flagged up.
Yet there are now some technical solutions that could help put the trafficking gangs out of business.
One man who is trying to change this is Kevin Montgomery of Stanford University, who has set up Collaborate.org.
Collaborate takes input from sources such as GIS (geographic information system) data, news and social media feeds, sensor networks, weather reports, shipping movements, and collates this in a single global mapping platform.
Its 3D world view then allows a user to zoom in on a location and see all the information there is about that place.
It currently has up to 10 petabytes worth of data - five times the information stored in all US academic research libraries - a figure which is increasing all the time.
"When you can bring all of those layers together, and everything that everyone knows about this problem together - you can really get some co-ordinated action planned," says Dr Montgomery.
Phoning for help
However, one basic problem for many modern slaves - is how to call for help.
Hugh Bradlow, the chief technology officer for the Australian telecoms firm, Telstra, is pushing for a single global emergency number for victims of slavery.
But there are various challenges to overcome first before there is a single global help.
"Often the people who are being trafficked don't know what country they are in, so it needs to be the same number in every country.
"They could be illiterate so they may not be able to use texts. They could be in a different language zone, so it needs to be multi-lingual."
Keeping callers safe from retribution is also vital.
"The people who are trafficking them have access to their phones, if they are using phones," says Mr Bradlow.
This means traffickers can see which numbers their captives are dialling or texting messages to.
He says the safest way to do this securely could lie with a relatively little-used piece of technology called USSD, or Unstructured Supplementary Services Data.
USSD is built in to all GSM (global system for mobile communications) phone signalling systems, and is a way of sending short commands from the mobile to the network.
Most commonly, USSD is used by prepaid phone users to check their available balance - the text messages can be up 80 characters in length.
"It's a very simple system, you put in a hash before and after a number, and then you press send - it doesn't leave a trace on the phone," says Mr Bradlow.
"On the receiving side it's very easy then to redirect that message globally and it tells you which network the phone is attached to and what home number it's got.
"And that would enable the local authorities in that country to go then and locate the phone."
Mr Bradlow hopes that this could be operational relatively soon.
"I wouldn't like to declare victory at this stage - globally you've got to get some changes made to the networks of different carriers - but it is feasible and not beyond the realms of cost."
'A pig is worth much more!'
For her part, now safely in Cambodia, Socheung says she is simply happy to be home.
"When in China, my life was hell - my life now is much better."
There is a curious coda to her story. The trafficking gang's leaders are now on the run, and if caught it will be Socheung's testimony that will be used as evidence against them.
Recently she got a call from the daughter of the gang's ringleader. It was an offer of a bribe if she dropped her case. The sum offered was insultingly low - just $50.
Socheung says she refused outright: "It's ridiculous - a pig is worth much more than this!"
For more on technological solutions to slavery, listen to Ed Butler on BBC World Service's Business Daily programme