By Katherine Sellgren BBC News education reporter

Bill Jenkins was abused whilst in care in the 1950s and 60s

Revelations about known sex offenders being allowed to teach in the classroom have heightened the need for vigilance. Many software packages on the market can block pupils' access to nudity, violence, drug and alcohol promotions.

Now packages which alert head teachers to what staff members are viewing are helping to root out would-be abusers.

One package, Securus, was set up by a computer expert who suffered abuse himself whilst in care as a child.

The reason we, the company, exist is because of what happened to me Bill Jenkins

Bill Jenkins has channelled his anger about his experiences into devising a software package to track down paedophiles.

Mr Jenkins wanted to find a way of stopping paedophiles who turn to computers to "groom" children or to access child pornography.

Use in schools

The Securus computer monitoring programme is being used by more than 300 schools across the UK and is expanding into the National Health Service; two hospitals have installed it on their PCs.

The software lists every website visited by users and monitors text in every application - on or offline, saved or not - having been programmed to pick up on key words and phrases.

"If there is any impropriety, Securus will take a snap shot of what's on the screen and save it. It then sends it with user name, PC number, date and offending word or phrase to the administrator," says Mr Jenkins.

The software also monitors school laptops if they are taken home: once plugged back into the school system the software highlights all of the activity carried out while the laptop was out of the school.

"Sometimes these people seem to think that if they take the school equipment away from the school, they are not being monitored," says Mr Jenkins.

"People are often reluctant to use their own equipment to access things of an inappropriate nature, so they use other people's."

Big Brother

As well as picking up on paedophilic activity, the software is programmed to track foul language, racism, terrorist activity, evidence of bullying and references to weapons and drugs.

But doesn't the application amount to "Big Brother" watching people?

The software monitors all activity, on and offline

"It's a frequently asked question," says Mr Jenkins.

"But Securus is only looking for inappropriate use - if you are behaving appropriately, you have nothing to be scared of."

And he stresses that, legally, people can only be monitored if they are made aware that the software is in place.

"It's just another tool to identify misuse on any PC and protect vulnerable people."

But at a typical cost of �6,000 to install in a school with 250 computers, many head teachers may find it is a tool they can ill afford.

Turning the past to good

Put into care at the age of three, Mr Jenkins suffered physical, sexual and mental abuse at the hand of his supposed carers.

"It was abusive care, there was no-one there for us, no-one listened," says Mr Jenkins.

"I kept running away. I was in distress. It was horrible, awful."

In 1971, at the age of 17, Mr Jenkins managed to get away from the abuse by joining the Navy.

"I went into the communications branch, which gave me a great understanding of technology. And being in the Navy kept me institutionalised in a positive way."

Mr Jenkins left the Navy in 1978, but what had gone on in his childhood still haunted and angered him.

He founded Securus Software Limited and, four years ago, the company launched the software package to pick up on inappropriate computer use.

"I wondered what I could do to protect children from this and that was the passion - it was all about protecting children from abuse, often hidden abuse and from people who don't care," says Mr Jenkins.

"The reason we, the company, exist is because of what happened to me."