More than 25,000 cyber attacks were carried out against Essex County Council in the past year, it has emerged.
It is thought those carrying out the attacks were attempting to access the personal details of people living in Essex, which are held by the authority.
The council refused to state whether any of the attempts were successful.
The council said it spent more than £500,000 each year employing a team of six people to protect its systems.
David Wilde, the authority's chief information officer, said: "We hold a lot of sensitive information on people, it is in the nature of our business.
"Also, and just as importantly, we hold a lot of information about our geography. You have to remember that Essex has one of the biggest military bases in the country with 16 Air Assault Brigade and we also have one of our international airports here."
Sensitive data held by councils include the addresses of children using home to school transport, the medical and care needs of the elderly and details of its employees.
In Essex, the county council employs 40,000 or so staff and teachers.
'Changing social habits'
The county council said there had been about 27,000 attacks on their computer systems in the past year.
It said there had been a slight increase in attacks in recent years.
Part of the reason for the attacks, said Mr Wilde, is that it holds a ".gov" website address. Organisations holding such website addresses are identifying themselves as government departments.
Businesses too are at risk, according to data protection experts.
Rafael Ruiz, a data protection lawyer at Birketts, said: "With new technology and changing social habits, more and more of us are using financial data to buy products online.
"More and more of our data is being held by the public sector and private businesses.
"The perception is that it is only the big international companies and public authorities that are targeted."
But, said Mr Ruiz, small businesses were also targeted and, if attacks were successful, could end up spending between £35,000 and £60,000 putting their breached systems right.
"Nothing is 100% safe and there is no 100% safe way of protecting it," he said.