Almost half of UK home broadband customers use wireless internet access but a staggering 19% of them are at risk because they haven't protected their networks with a password.
In fact, one in four people questioned on behalf of moneysupermarket.com didn't know that anyone close enough to their router can use an unprotected wireless network without the owner's consent - or even knowledge.
Yet more than four million people admitted hijacking someone else's wireless network in the last 12 months.
Of course, most of those people simply want to use the internet without paying, rather than steal your data or commit crimes - the most common reason for hijacking a connection is just to browse the web.
This can slow down your own web use but there are also more serious threats.
One common risk if other people are using your web access is that you will go over your provider's download cap - meaning you could be hit with a huge bill for other people's downloads!
However, there are more sinister risks. There are some crooks who will use a household's web connection to download obscene content or even steal your data and commit identity theft.
James Parker, moneysupermarket.com's broadband expert, said: "The consequences of hijacking can be severe. It's bad enough your neighbours can use your internet connection freely, but this becomes far more threatening if someone uses your connection for criminal or improper activity."
Beat the thieves
There are several ways for you to make sure your wireless network is only being used by your household and they aren't complicated or overly technical. Here's moneysupermarket.com's top tips.
Know your limitsCheck up on exactly what your download limits are and work out what that means to you - for example, five music albums or a certain amount of content streaming.
Use a passwordProtect your internet connection with a password and don't make it too easy. It's best to use a mix of letters and numbers, preferably not dictionary words.
Keep an eye on the kidsIf you have children in the house, you might want to invest in some parental controls as well as password protection for the router. That way you can be confident your youngsters aren't exposed to anything they shouldn't be. Check your routerTo be as secure as possible, you should have a router that uses 'wifi protected access' (WPA) rather than 'wired equivalent protection' (WEP) encryption.
If you aren't a tech-head then don't panic, this isn't as complicated as it sounds. WPA is the new security standard and is less open to abuse, so it's worth investing in a router that gives you this additional protection. Staying safe online
Unfortunately, the web does carry some risk and there are some clever cybercriminals out there. When you're online, especially if you're shopping or banking, it's worth taking a few moments to double check you're safe.
Shop for some softwareTo keep your sensitive data as safe as possible, make sure you are using up-to-date anti-virus and firewall software.
Watch out for phishing attacksDon't open links in unsolicited emails and definitely don't give anyone you don't know your details. Your bank will not email asking you for your PIN or other information.
Be warned that not all phishing messages are as obvious as the Nigerian lottery win, some can be very convincing and look like a message from your bank.
Beware bogus sitesIf you're carrying out any kind of financial transaction on the web, make sure the site is genuine and secure.
If you're about to enter your card details then check for a padlock symbol on your browser first - that means it's secure. Be careful, though, a padlock on the actual web page is meaningless, anyone could have added it.
For some detailed advice on shopping safely online, read our article '
Stay safe online this Christmastime'. Switching your broadband
Of course, if you're confident that your network is safe and secure but it's still running slowly, it might be time to move providers and find a better service.
Read our article '
Beware the broadband traps' for a guide on finding the speed you need and watch our video ' How to switch broadband provider' to see how easy it is to move.
Rate This Article
Click on a star to rate this article.