A prototype AI that spots online trolling can be tricked with a few typos, researchers have shown.
The system, from Google spin-off company Jigsaw, fails to detect words like "idiot" and "stupid" as toxic language when misspelled as "idiiot" or "st.upid", for example.
Jigsaw said its tool, called Perspective, was still in development.
One computer scientist said such systems would always have to adapt to the changing tactics of trolls.
Jigsaw's tool is being developed to help automate the detection of abuse and harassment online.
"Perspective scores comments based on the perceived impact a comment might have on a conversation," the Jigsaw website says.
But researchers from the University of Washington, whose paper has not yet been peer-reviewed, found the system was far from infallible.
While the AI graded certain phrases as toxic, almost identical ones could sneak by with just a few creative typos:
- "They are liberal idiots who are uneducated" (90% toxicity score)
- "They are liberal i.diots who are un.educated" (15% toxicity score)
There were false positive examples as well - in which innocuous phrases (such as "It's not stupid and wrong") were erroneously graded as toxic.
The findings were welcomed by Jigsaw.
"It's great to see research like this," product manager CJ Adams told technology news site Ars Technica.
"We welcome academic researchers to join our research efforts on Github and explore how we can collaborate together to identify shortcomings of existing models and find ways to improve them."
Accounting for "adversarial examples" - deliberate attempts to fool a system - was a key part of developing such systems, said computer scientist Dr Pete Burnap, at Cardiff University.
"These things are typical problems in natural language processing," he told the BBC.
"Jigsaw will probably look at this and start incorporating adversarial examples into their training set."
He said he was pleased to see companies such as Google working on technology that might one day help curb trolling online.
"It's really great actually to see companies like this come forward and say, 'Here's a toxic comment,'" Dr Burnap said.
"[Such comments] can harm people and communities."