This type of fraud, known by terms including ‘phreaking’, ‘toll fraud’ or ‘dial through fraud’ sees cyber-criminals exploit technology such as business phone systems.
Hackers get access into the system and divert the voicemail through to an inflated premium rate number at the expense of the business.
They run up huge bills on premium numbers that they control and it is turning into a growing business for organised crime groups.
Bills will depend both on the number of calls and how long the fraud has occurred for before detection.
The Business Crime Reduction Centre recently stated it knew of companies that had faced charges ranging from £1,000 to £90,000.
The UK is ranked in the top five global countries for business telephone fraud and the BBC reports it costs UK businesses approximately £1.5 billion per year – with the global cost estimated at over £3 billion.
Businesses are advised to disable divert facilities and regularly change the PIN on voicemail systems to avoid falling foul of the hackers.
Other security measures include setting charge limits or asking a telephone provider regarding tools available to reduce the risk of fraud.
Businesses that rarely make or receive international or premium calls can often get these types of call blocked or diverted by their supplier.