Police have issued a warning about an online shopping scam in the run up to Christmas.

Hertfordshire Constabulary said fraudsters have been taking advantage of people’s tendency to sign for packages upon delivery without checking the contents.

Shoppers caught out by the scam then discover that the package is empty or is not what they ordered.

Investigators said because the item had been signed for, victims then have problems disputing the transaction with the online vendor, as the tracking information indicates that the ordered item has been delivered and signed for.

The National Fraud Intelligence Bureau is investigating the scam.

How to avoid being caught out:

1. Always check seller feedback when buying online – if the seller has a lot of recent negative feedback, do not buy from them. It is not unknown for fraudsters to hack legitimate accounts or trick legitimate sellers into allowing them to use their account for fraudulent purposes, so focus on the most recent feedback.

2. Consider keeping a list of which items you and the people you live with are expecting to be delivered, as it can be particularly confusing when you have a large number of items on the way, which is often the case in the run up to Christmas.

3. If you are asked to sign for a package and are in any doubt as to what it is for, consider opening and verifying it before signing for the item.

4. If you, or anyone you know, have been affected by this fraud or any other scam, report it to Action Fraud by calling 0300 123 2040 or visit www.actionfraud.police.uk.

Detective Inspector Yvonne Lewis of the Cyber and Financial Investigation unit said: "The number of people shopping online increases dramatically in the run up to Christmas. Cyber criminals are keen to take advantage of this increased online traffic and this particular scam is something all online shoppers need to be aware of.

"These are some simple steps that can be taken to avoid falling victim to this scam. It’s also crucial to ensure that there is a green padlock symbol in the security status bar when completing online transactions. Also wherever possible try to make purchases from reputable companies that you trust. 

"If you get emails offering goods for sale, be careful about clicking on links to purchase these goods, as cyber criminals send out emails with links to bogus sites that look like they are legitimate. 

"If you want to visit the site use a search engine and type in the name of the store, so you are sure you are visiting the genuine website."