The scam goes something like this:
You're surfing away on the Internet and, on clicking a link, you are presented with a page (or pop-up window) that has wording similar to:
WARNING!! Your computer is currently broadcasting the following Internet Address: [your IP address is shown here].
Every time you connect to the Internet, send an email or submit private information to a web site, you are broadcasting this unique address.
With this address, someone can immediately begin attacking your computer. Download (Name of the product being "pushed" here) to protect yourself now!
Often there will be a advert for the product and the page is frozen until you click OK.
There is no need to worry about this at all! If your computer didn't transmit your IP Address then you would never get anything from the Internet! The IP Adress is the information that the server requires to send you the page, image, sound file, email etc. that you wish to see.
Think of it this way: If you phoned a company and asked for a catalogue would you expect to receive it if you didn't tell them where to send it?
This type of scam is just scaremongering. Often the software that is "offered" is loaded with key loggers and tracking software that reports back to the vendor where you've been and what you typed in, email passwords, bank login details etc., viruses and programs that allow external control of your PC could also be hiding away in that piece of "protection software"!
The scare tactic is a good one to use on the unknowing as they think that they will be safe on-line after getting this product but, if it did what it claimed (block your IP Address), then your Internet use would be at an end! (A bit like becoming homeless so your house can't be burgled).
The best way to deal with this, if it has "locked" your browser, is to click OK and then, before the download starts, close the browser window.
If it is a pop-up window that is offering this then just close that pop-up window, if you can - if not follow the above advice.
There are methods that unscrupulous people could use to gain access to your PC using the IP Address but any half decent Firewall / Anti Virus / Internet Security Suite will stop intrusions like this before they start.
I would go further to say:
Never download any program that tells you that you have a problem unless you actually went to their website deliberately to scan for a problem that you already thought you had. Even then only if it was a reputable company (AVG, Kaspersky, McAfee, Panda, Symantec, Trend Micro etc.)!