Helping people with computers... one answer at a time.
When scanning for wireless connections you may find several that are unknown yet and appear open and available. Using them is risky. Very risky.
My internet connection went down on a Friday, and the service rep gave me a service call time for Monday, maybe. My HP notebook has wireless capability so I turned it on and checked what wireless networks were available. There are 3 secured and 1 unsecured wireless networks. I am able to logon to the unsecured wireless network, a NETGEAR network. The signal is low and only about 500K but works. Am I breaking the law by using someone else's wireless network? Is there a way to find out where this wireless network is and who owns it, hopefully it is a free public wireless network? Am I in any danger from using this wireless network? I am not doing anything that requires a password, and I have Windows Firewall, Norton antivirus, and Windows Defender running on my computer.
What you're doing is very common. With so many open wireless hotspots around it's a temptation that's frequently too hard to resist, particularly when you're in need.
And yet, resist it you should.
There are a number of problems that arise from connecting to an unknown but open hotspot.
I actually don't have a definitive approach to identifying the owner of an open hotspot. The access point name that's displayed is often a clue, I suppose, but clearly the person who set up the open hotspot you're seeing didn't bother to change the default name, so that's no help at all.
There's just no reliable way to know for sure, without more information.
So we'll simply assume it's a poorly configured access point in someone's home or business.
Now, I am not a lawyer, so I'm certainly not giving out legal advice. But I would guess that it's highly likely that what you're doing is, in fact, illegal in most places. Naturally, laws and enforcement vary greatly from location to location.
I have no idea what the law is in your situation, but it's safest to assume that it's illegal.
At a practical level, though, legality may not be your biggest issue.
When you connect to the internet, the owner of the connection could pretty much see everything you do.
Most of the time you have no need to really be concerned. Your "real" ISP (the one you're paying money to, and the one who's apparently coming out on Monday) typically doesn't care. When you visit a friend, they probably don't care. When you visit a coffee shop or hotel with free internet, they probably don't care.
But they could.
If the person down the street notices that his internet has slowed to a crawl at unexpected times he will care. And if he's tech savvy at all, he might well be able to peek at what you're doing. Even with a simple router or access point it's not that difficult to set up a PC with some software to monitor traffic. It'll be complex data that's perhaps difficult for a lay person to interpret completely, but it's easy to watch and easy to capture. And with some serious computer savvy it's also possible to mess with.
Let's consider a different risk: malware, and liability.
You've got your computer's firewall up, and that's great, but you're still exposing yourself to an unknown network. In fact, I'd claim that since that network has no wireless password it's likely that the person operating it is less technically savvy than you are. You're about to trust their having set up their network properly and securely, and the one data point you have says that's not very likely.
I certainly hope you have a good firewall, as well as anti-malware and backup solutions.
Looking at it in a different light, what happens if you accidentally have malware already and it ends up infecting one of the machines on this unknown network? Once again, I'm no lawyer, but I'd expect it's possible for some serious liability issues to arise should you be discovered as the source.
Finally, there's another even more troubling scenario. Hackers have been known to set up open Wifi hotspots specifically to lure in unsuspecting victims, and then monitor their internet traffic and steal valuable information or worse.
As you can probably predict by now, here's my suggestion: don't do it. Just don't. There's simply too much risk, both legal and technical, if you head down that path.
If you must, if you just can't help yourself or if you've discovered that you're connecting to a legitimate, legally accessible public Wifi hotspot, then of course you do need to treat it as you would any open hotspot: How do I stay safe in an internet cafe?
In your shoes, I'd wait 'till Monday, or perhaps visit a trusted friend.