Two men from Watford and one from Rickmansworth have been arrested in a covert police operation targeting people accessing indecent images of children online.
The six-month operation to identify and prosecute sex offenders was kept secret until today to protect children and secure evidence.
Hertfordshire Constabulary used polygraph tests and tracked the activity of offenders to follow those who furthered the sexual abuse of children by downloading and sharing indecent images continues.
In total, seven men were arrested across the county as part of a national crackdown.
The men arrested are all currently on police bail having been questioned on suspicion of possession of indecent images.
A 27-year-old man from Watford has been bailed until July 25, a 63-year-old man from Watford has been bailed until November 12 and a 45-year-old man from Rickmansworth has been bailed until November 17.
Officers from the force's dedicated Child Online Safeguarding Team are investigating.
DCI Stuart Orton said: "Our work to tackle these crimes and bring offenders to justice is very much on-going and we are continually carrying out proactive operations.
"These offenders actively promote the continued sexual abuse of children by downloading and distributing indecent images.
"They may think they are ‘invisible’ because they are alone and online, but they are not and we will use every power available to us to target those involved and ultimately safeguard children within Hertfordshire and around the world.
"I would like to take this opportunity to encourage anyone who has any information about those who are committing these offences to contact officers in COST via the Herts Police non-emergency number 101."