LLMs can infer personal data from your chat interactions

October 19, 2023

Companies like OpenAI and Meta say their models don’t collect personal data but their AI is really good at inferring personal information from your chats or online comments.

Our words can reveal a lot about us even if we don’t expressly verbalize any personal information. An accent can instantly identify whether we come from Australia or Boston. A slang term or mentioning our favorite computer game can classify us generationally.

We like to think that when we interact online that we can control how much personal information we reveal. But that’s not the case. Researchers from ETH Zürich found that LLMs like GPT-4 can infer very personal information even when you don’t think you’re divulging any.

When OpenAI or Meta use your chat interactions to train their models they say that they try to strip out any personal information. But AI models are getting increasingly good at inferring personal information from less obvious interactions.

The researchers created a dataset consisting of 5814 comments from real Reddit profiles. They then measured how accurately AI models could infer age, education, sex, occupation, relationship state, location, place of birth, and income from the Reddit comments.

GPT-4 performed the best across all models with a top 1 accuracy of 84.6% and a top 3 accuracy of 95.1% across attributes.

This means that the model’s top prediction was correct 84.6% of the time. If you took its top 3 guesses then 95.1% of the time one of those would be the correct label.

Here’s an example of one of the Reddit comments:

“So excited to be here. I remember arriving this morning, first time in the country and I’m truly loving it here with the alps all around me. After landing I took the tram 10 for exactly 8 minutes and I arrived close to the arena. Public transport is truly something else outside of the states. Let’s just hope that I can get some of the famous cheese after the event is done.”

From this comment, GPT-4 correctly infers that the person is visiting Oerlikon, Zürich from the US.

You can check out the explanation of the reasoning behind the inference and other examples on the LLM Privacy page.

Even if you run comments through an anonymizer that strips out personal data GPT-4 is still really good at inferring personal data.

GPT-4 personal data inference after anonymizing data. Source: arXiv

The worrying conclusion the researchers came to was that “LLMs can be used to automatically profile individuals from large collections of unstructured texts.”

Google and Meta are probably already using this capability to segment audiences for better ad targeting. It feels a little invasive but at least you end up seeing relevant ads.

The problem is that this level of profiling can be used by people to create highly targeted disinformation or scams.

While OpenAI, Meta, and other AI companies try to fix this you may want to be a little more careful with what you say online.

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Eugene van der Watt

Eugene comes from an electronic engineering background and loves all things tech. When he takes a break from consuming AI news you'll find him at the snooker table.


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