'What the hell is this?" asked a friend of mine the other day, handing me his mobile. "It's a Sony Ericsson," I replied. He sighed, and wearily pointed at the text message on its screen, which read: "You have a sexy admirer. Call this number to hear their message!"

We quickly deduced that no sexy admirer was behind this, and that the invitation was just a ruse to prise some cash out of him. SMS spam isn't as rife as email spam – indeed, there doesn't seem to be a word for it yet (m-spam? SpaSMS?) trouble is, you can't tell if it's spam unless you read it. Your first reaction is to wonder who or what is responsible (answer: a computer program via an internet gateway) and then how the spammer got your number.

While some spam is fired off to random numbers, we do tend to reveal our number to organisations and then forget we've done so. "I've just been spammed by Avon and Somerset Constabulary," emailed Gemma Cossins at the weekend.

"I signed up for Glastonbury alerts last year, but despite sending STOP messages, I keep getting notes telling me that the A39 is shut." So, how to fight back against the more pernicious messages? Firstly, make a fuss. If a premium rate number is advertised, complain to regulator PhonePayPlus on 0800 500 212. Or call your network; a spokesman for 3 advised us of an occasion where they managed to prevent SMS spammers gaining any revenue from a message – that action was as a result of customer complaints.

Secondly, don't be tempted to act on its contents. Mark Harris, director of security experts Sophos Labs, makes the indisputable point that if spammers fail to make money from SMS, they'll give up. Oh, and be thankful you're not living in the US where you actually have to pay for the privilege of receiving each of these irksome notes.

Diagnosis required

Email any technology gripes to cyberclinic@independent.co.uk, or join the discussions on the blog at www.independent.co.uk/cyberclinic. Currently under discussion: Is internet addiction a mental illness?