SCAMS are costing northern beaches residents thousands of dollars every week, with police urging people to use secure websites to make payments.
Victims, many looking to buy a puppy or used mobile phone, often transfer money to the supposed seller without taking proper precautions, police say.
"If you think it's too good to be true it probably is," Crime manager Detective Inspector Michael Boutouridis said.
"The seller says 'deposit the money into my account and as soon as the money's there I'll send you the item'. Then the seller is no longer contactable," Det Insp Boutouridis said.
He said buyers should be cautious if they are unable to meet the seller to purchase the item.
"The easiest way to deal with someone is to use an escrow account [such as PayPal]. It's a third party account that retains money on behalf of a buyer and will only release the money to the seller once the buyer has received the item," he said.
"It also gives you someone to contact if you don't receive the item."
For more information visit Scam Watch.
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