One lawyer with pro-democracy leanings messaged an AFP journalist asking for their entire WhatsApp history to be deleted.
Another announced they were moving all communications to Signal, which they felt was a more secure messaging app.
Beijing has said some serious cases will be prosecuted on the mainland, dismantling the legal firewall that has existed between Hong Kong’s judiciary and China’s Communist Party-controlled courts since the 1997 handover from Britain.
Local police have been granted wider surveillance powers to monitor suspects, including wiretapping and accessing digital communications, without a judge’s approval.
The new law also allows China’s feared security agencies to set up shop in Hong Kong for the first time.
Beijing says it can now prosecute national security crimes committed outside it borders — even by foreigners — raising concerns that people visiting of transiting through Hong Kong could be arrested.
Companies providing virtual private network (VPN) tools — which can make internet access more secure — have reported a spike in downloads since the law was announced.
Billie, a 24-year-old assistant to a district councillor, said he started using a VPN in May when China announced plans for the new law.
He culled many of his social media followers and removed some “sensitive” posts — even though Beijing’s new law is not supposed to be retroactive.
“I feel very ashamed and embarrassed. I never wanted to do so, but I felt I have to, in order to survive,” he told AFP, also asking for anonymity.
“A part of me is gone.”