Spark customers are being warned that phone scammers posing as telco staff are once again on the prowl.

Fraudsters are reportedly telling people their services will be cut off due to security issues unless they clean up their computers or change settings.

Customers are being warned not to engage with phone scammers and hang up immediately.

They are then directed to a fake website where they are asked to download software, give the caller remote access to their computer, or divulge their banking details.

Another form of the scam involves telling people they have exceeded their data limit, and need to provide their credit card details to cover the cost.

Spark general manager customer service Bridgette Dalzell says it is crucial customers do not hand over their personal information.

'We will never ring customers out of the blue and ask them for personal information such as bank details or passwords.”

Anyone who received such a call should hang up as soon as possible.

Scammers are going to great lengths to hoodwink their victims, sometimes instructing them to leave their phone off the hook for several days, or providing a made-up employee number.

Bridgette says the scammers did not have access to Spark's systems.

'These fraudsters appear to be actively monitoring our activity and copying our methods of communication, so we know it can be difficult for customers to tell the difference between genuine calls and fake ones.”

She urges anyone who suspects they are a victim of the scam to contact their bank immediately.

The telco company warned of the same predatory behaviour a year ago, after at least one customer had money taken from their account.

Spark spokeswoman Lucy Fullarton says it was rare that people fell for the scams, but when they did, they tended to lose 'quite a bit of money”.

The company did not have information on how many victims were taken in, but she had not heard of any cases recently.

Cyber-safety organisation NetSafe recently said phone scams were on the rise again, with uglier tactics than ever before.

Many were so-called "tech support" scams, where the caller usually claimed they were working for Microsoft.

Chief executive Martin Cocker says the scams came in waves, with the callers working their way through a list of numbers.

"NetSafe might see a dozen to 20 calls a month on a quiet month, and then it'll rise up over 100 on a busy month.

"Of course, that's only a fraction of the reported calls, that's just people who report it through to us."

Cocker encouraged people to alert friends and family, as some vulnerable people did lose substantial sums of money through such scams.

NETSAFE'S ADVICE FOR DEALING WITH COLD CALLERS:

• Hang up. Engaging with or taunting companies can lead to you receiving many more calls at all times of the day or night. Some technicians have resorted to threats or abuse to get computer owners to give remote access.

• If you do give access but become suspicious, disconnect the machine from the internet immediately.

• If you have previously given remote access, it may pay to check what has been installed on your computer and be certain there is no way for the company to continue accessing your system and files.

• If you have paid money to these companies using a credit card, call your bank and discuss your options.