The internet is making it a lot easier to fake who you are via the phone.

Many online services are springing up that bypass Caller-ID and can make it look like you are ringing from almost any phone number.

The spoofing services work with mobile phones, landlines as well as telephone services that are routed via the net.

Though spoofing Caller-ID is not illegal there are already reports that conmen are using it to give bogus calls more credibility.

Number game

Since it was introduced Caller-ID or Call Line Identification (CLID) has helped people work out who is on the end of the line by displaying the number of who is calling them.

Many companies use CLID data so when you ring a customer helpline, your details are automatically sent to the computer of the staff member who takes your call.

But some US net-based firms are now offering a spoofing service that lets people choose the number they are calling from.

At least seven firms have set up shop on the net offering these spoofing services. Four are aimed at consumers and another three restrict themselves to helping law enforcement agencies and private investigators.

One of the first Called-ID spoofing services Star38 shut down soon after it set up in August 2004 following the negative reaction to its debut. Subsequently the company has been bought and has re-appeared under the same name.

There is nothing to suggest that the firm Star38 is being used by specifically by conmen to fake phone numbers.

Using the faking systems typically involves ringing a freephone number then tapping in the number you want your call to look like it is coming from and who you want to call. Some make users fill in a web form for the number they want to call and spoof.

Prices can be as low as a few US cents per minute.

Although based in the US, some services can spoof calls internationally too though it is unclear whether the service will work flawlessly across long distances.

A spokesman for Telespoof said that the publicity surrounding Star38 has driven others to set up their own services.

Technology developments have also driven down the cost of setting up such a service, the spokesman added.

Most of the cheaper Caller-ID faking services market themselves as a way for users to play tricks on their friends.

However, there are already reports that conmen are abusing the ability to fake Caller-ID to make bogus phone calls look like they are coming from a legitimate and trustworthy company.

Simply faking a phone number is not illegal in the US or the UK.

A spokesman for the Ofcom, the UK's telecom watchdog, said it had received only one call about Caller-ID spoofing from someone concerned about what would happen if it took off in the UK.

Widely-accepted industry guidelines dictate that people are honest in their use of CLID, he said

But, the spokesman said, Ofcom was a complaint led organisation and would move to investigate if it got a lot of enquiries from consumers about people or organisations systematically abusing the system.

"We are aware of it and are monitoring the issue," he said.