Some time ago tweets started to appear on Twitter to the effect that Facebook was no longer going to be free to use after a certain date. Not true, of course. Now similar tweets are being bandied around, saying that Twitter is going to start charging its members. "Sign the petition" or "Read more" say the tweets and, indeed, it's tempting to do so. However, even though the links given look authentic (having been shortened by bit.ly) they actually lead to a potential source of malware. If you click and your computer isn't protected, you could be in trouble.
I discovered some time ago how important it is to have anti-malware software as well as anti-viral software. A piece of malware got onto my computer and I had an awful time trying to remove it. A pop-up box kept appearing telling me that my computer was infected and that if I clicked the link and paid however much was being requested, I would get access to software to remove the infection. Of course, it was the pop-up box itself that was the malware . . . but I've heard of people who, in desperation, did pay up in order to have it turned off.
I was fortunate in that I have access to a second computer. Using this, I searched for some information about the pop-up box and its demand for money. It led to me to Malwarebytes.org where there were instructions on how to remove it, without having to pay any money to anybody. After that, I installed Malwarebytes software. Since then, on several occasions, it's stopped me from going to potentially dangerous sites. After all, one url looks much like another, particularly if it's been shortened to fit into a tweet. So it's becoming easier and easier to click on a dangerous link by mistake.
I find it sad that there are, apparently, so many people 'out there' trying to disrupt other people's computers. But I'm profoundly grateful that there are some equally clever people who are dedicated to keeping our computers safe.