SECRET listening devices and cameras are becoming more common and harder to locate, a cyber-security firm has warned.

Devices which cost a few pounds to buy require kit worth upwards of £10,000 to find, according to Poole-based C3IA Solutions.

The company, which has a growing technical surveillance counter measures (TSCM) department, is training new staff in the skills required.

It says bugs come disguised in everyday objects such as smoke alarms, plug sockets, air fresheners, clocks and calculators, as well as in other devices that can be easily hidden.

Many devices are noise-activated and dial your phone when someone speaks, so a private conversation or meeting can be monitored form anywhere in the world.

The company says the users of bugs range from rogue states to people who suspect a spouse is hiding something from them.

C3IA works in the UK and abroad for governments, businesses and high net worth individuals.

Security director Matt Horan said: “Our TSCM work – or bug-sweeping – is a growing part of the business.

“We often speak to companies about their cyber-security and when we show them what devices are available for just a few pounds, it really focuses their minds.

“Often we are called in when someone suspects that private information has been compromised. Finding these devices is difficult because they are so small and so well disguised.

“We have equipment worth tens of thousands of pounds so we can locate them, but it still requires us to shuffle about in attics and cupboards – often in the dead of night.

“We’re regularly called in by companies to check their boardrooms and meeting rooms, and we are sweeping more superyachts.

“High net worth individuals regularly need their properties and cars checking because every time there is a visitor or workman, a device might have been planted.

“It might seem like paranoia but in fact these devices pose a real and genuine threat.

“Those who plant them could be seeking a rival’s information, but might also just want to learn passwords and email addresses to use for fraud.

“With these devices so cheap and easily purchased over the internet, it makes eavesdropping incredibly simple.”