Business telecommunications and IT systems

In the same way that a new virus causes havoc, telephone voice mail systems are the latest targets for hackers who can make significant profits at the company's cost.

The hacker will call company after company until they are answered by a voicemail system. Using the latest password hacking techniques, they obtain access to the administrator options and alter the settings.

By activating an unused extension and setting Call Forward to Exchange Line, the scam is ready.

The hacker now re-dials the company and is answered by the voicemail. Then they dial the unused extension whereupon the voicemail directs their call to an exchange line, allowing the hacker to dial wherever and whatever he wants at the expense of the company. Premium rate numbers are a favourite.

Normally, the company would not know anything was amiss until they saw their next large phone bill. Given the normal time interval between bills, the costs can mount to many thousands within a very short period of time.

Apart from a hacker having 'phone call freedom', they often sell the number sequence. When this happens, the use and cost can quickly escalate.

BT has a department which can trace calls even if the Caller ID has been withheld. BT will liaise directly with the Police to see what can be done. However, there is no recourse about the costs of the calls - the company has to pay.

Ensure you have the latest software update for the voicemail system, and tie the controls down as far as they will go, thereby making it hard for the hacker to crack.

Normally this involves a visit form the system maintainer since extensive knowledge of the system is vital, as well as having the latest software to hand.