Worried residents across York have joined the Facebook group, called Find the Westfield Attacker, after the 18-year-old victim was raped as she walked home on the outskirts of the city.
The severity of the attack has shocked residents, and the officer leading the inquiry, Det Supt Lewis Raw, has said it was the worst offence he had seen in 28 years.
Now 1,640 people have joined the online group, set up by local resident Ashley Parker, who lived for 20 years in Westfield Place, near where the attack took place.
Members are using the site to post updates about new leads and discuss putting up posters of the police e-fit and attending self-defence classes.
Female members have also posted messages saying they are following a warning from North Yorkshire Police not to go out alone at night.
Mr Parker said: "The whole point of the group is to make people aware of the crime which got committed last week and keep residents and the general public updated on current goings on.
"It's the rapist who should be worried."
The victim was attacked early in the evening on Saturday February 20.
She had finished work at a city centre cafe and caught a bus home before being attacked while walking across a field off Grange Lane in Acomb.