KNOW your customer. It is the mantra of every salesman. And this same lesson has been learned by the con artists who fleece money from a nave public.

Householders who respond to one "get rich quick" scheme soon become targeted for many more. The reason? Their details are circulated around the burgeoning scam sector.

In legitimate business, the sale of mailing lists is common practice. The names and addresses of consumers whose previous purchasing patterns make them more inclined towards certain products and services are a valuable commodity.

Now firms who prey on the more trusting among us are doing the same. North Yorkshire Trading Standards department warned today that someone who falls for one dodgy scheme is placed on what is nicknamed the "suckers list". They are then likely to be bombarded with many more.

The scams come in all forms but essentially they boil down to the same thing: a promise, always unfulfilled, of a wonderful reward - as long as the customer responds immediately, enclosing hard cash.

It is hard not to have a grudging admiration for the ingenuity behind these schemes. The perpetrators are never short of an idea.

And they are quick to turn new technology to their advantage. In recent weeks we have reported on scams perpetrated by post, fax and mobile phone text message. Many people with an email address are wearily familiar with messages purporting to be from former African leaders, who promise a share of their wealth if we simply forward an administrative payment.

Most of us simply ignore the scams. But for elderly people, and others on low incomes, promises of instant prizes can be hard to resist. In some cases, they have lost their life-savings.

We applaud the trading standards teams' work to protect vulnerable people from the swindlers. And we can only reiterate their message: if a deal looks too good to be true, it is.

Updated: 11:34 Friday, July 04, 2003