Young webcam users are being warned not to fall for blackmail schemes following the second incident in two weeks involving male students who were filmed stripping online.
This comes as IT experts also warned that hackers looking for extortion targets can break into computer systems and steal intimate exchanges on webcam chats.
Police are investigating an incident in which an 18-year-old Hong Kong University of Science and Technology student was allegedly being forced to pay HK$5,000 by his female online partner after he was filmed nude in his room at the university hostel.
It follows another incident late last month when a 20-year-old associate degree student allegedly paid HK$7,000 to another female chat partner after being recorded taking off his clothes at home.
Police said they have received 41 complaints from January to October in which victims said they were blackmailed after being photographed or filmed naked or committing indecent acts.
The tip about hackers came from Karl Leung, head of information and communications technology at Hong Kong Institute of Vocational Education (Tuen Mun), in a warning for those who frequent chat rooms in search of new friends.
Hackers posing as friendly chatters can take control of users' computer systems and webcams, he said.
Leung warned people online to look out for signs of intrusions, including when images on the monitors "are not live."
Roy Ko Wai-tak, manager of the Hong Kong Computer Emergency Response Team Coordination Centre, said: "Third parties can detect which webcams are activated and watch targeted people through various communication software such as Skype."