Security systems that use biometrics such as fingerprint scanning are not fool-proof after all. This was proven by a Brazilian doctor who used silicone digits to sign in fellow physicians who were absent from work.

However, companies and government offices that use such a technology could still beat cheaters like 29-year-old Thuanes Nunes Ferreira who was caught by CCTV cameras using six fake fingers.

Police in Ferraz de Vasconcelos near Sao Paolo in Brazil arrested Ms Ferreira over the weekend in response to a tip received. They confiscated from her the six artificial limbs. They said the group behind the scheme involves 11 doctors and 20 nurses.

While she admitted to the charge of falsification of public document, mainly the time in and out entries of her colleagues, Ms Ferreira said the act of signing in for fellow workers at the Office of Mobile Emergency Care (Samu) was a prerequisite for her employment.

She pointed to Jorge Cury, coordinator of Samu, as the mastermind of the scam. Mr Cury, however, denied the charge and insisted he was not aware of the irregularity.

The arrest of Ms Ferreira, however, appears to be the tip of the iceberg. Acir Fillo, mayor of Ferraz de Vasconcelos, said up to 300 public employees in the city are considered ghost employees, or those who don't go to work but draw salaries. He said the ghost workers were spread in the health, security and education units of the city.

As a result of the arrest, the number of doctors at Samu dropped to 10 from 15, while Brazil's Health Ministry began an audit of Samu.