A rise in keyless car thefts across Hertfordshire has prompted police to issue advice on how residents can protect their vehicles.

Keyless car theft is where a vehicle is stolen without the thief taking or getting physical access to the key.

Criminals use a signal boosting device to detect the vehicle's vicinity key, which tricks the internal computer into thinking the key is present, when it is not.

The crime is committed without the thief entering the property - they simply detect the key's signal from outside.

Inspector Nicola Dean, from Hertfordshire Constabulary's Crime Reduction Unit, said: "Criminals are continually updating their tactics and are using technology to bypass keyless fob systems - allowing them to gain access and steal vehicles.

"You should get into the habit of storing your fob as far away from your vehicle as possible when at home. Placing keyless fobs in a metal box or faraday pouch will make your vehicle even safer."

Herts police have also issued further advice to help you protect your vehicle:

- Keep vicinity vehicle keys in a signal blocking pouch. You can purchase police approved 'Secured By Design' pouches by visiting www.securedbydesign.com- Keep key away from the front of your property - either upstairs or hidden away is preferable.

- Check your manual or with your dealer if it is possible to switch the key's signal off.

- For additional security, consider purchasing a steering wheel lock.

- If your vehicle has an alarm or immobiliser, ensure these are enabled.

- If your vehicle doesn't have a tracker, consider getting one fitted. Fit a dual band tracking device that works on VHF/UHF and GPS to ensure that one tracking system is still functioning if criminals use GPS blocking techniques to avoid detection.

- Sometimes vehicles are stolen when thieves jam the remote-door locking frequency by using specialist jamming equipment. They then enter the vehicle and clone a key from the On Board Diagnostic (OBD) port using specialist software. To help prevent this crime, consider fitting an 'OBD safe' device, a secure lockable device that fits over the vehicle's on board diagnostic port, in the vehicle cabin. This prevents criminals using software to code a key from the vehicle. We recommend devices that are 'Thatcham' approved, "Sold Secure", or "Secured By Design".