Until police officers came to arrest Guo Baofeng last July, the mainland blogger never imagined he would get in trouble by simply posting a video on the internet. Up to seven bloggers - including three who were tried on 'false allegations with intent to harm' late last year - had been detained for posting messages that claimed a young woman in Fujian province had been gang-raped and murdered by men who had connections with local officials. Just 20 days after Guo posted an interview with the mother of the victim on US-based photo and video sharing website tinypic.com, he was arrested. 'I never thought they would actually arrest me,' said 25-year-old Guo, who spent 16 days in a police detention centre. 'I think they were angry because I posted the interview on a foreign website.' Guo, known to thousands of followers on Twitter as Amoiist, believes the authorities had used passwords stored on his confiscated computer to access and delete the interview from the website. His blog on Google's blogger.com was also deleted. But how did the authorities know he had posted the interview online? Guo believes police were monitoring his conversations on QQ, an internet-based instant messaging system, with one of the whistle-blowers. 'I still have this sense of fear - I always worry how my e-mail messages would affect my own and other people's safety,' he said. Guo's story is just the tip of the iceberg of just how far-reaching government surveillance is on people whom it sees as a threat. The government's heavy investment on surveillance technology means human rights activists, journalists and lawyers increasingly feel the omnipresence of Big Brother. For veteran activist Qi Zhiyong , who lost his leg during the crackdown on the pro-democracy protests at Tiananmen Square in 1989, around-the-clock surveillance is just part of life. He is often detained by police on sensitive political dates, but the authorities have also made it clear that he is constantly monitored through his mobile phone and e-mail messages. 'The police said: 'Whenever you send messages on the computer, we know',' Qi said by phone. Qi recounted an occasion last year when a foreign reporter arranged on the phone to meet him. By the time the reporter arrived at his home, the police had taken Qi away. Gao Yu , a dissident journalist, said her phone calls are monitored and sometimes even cut off in the middle of conversation. On one occasion, she arranged on the phone to meet friends at a restaurant and four plain-clothes police turned up.