If your PC has been behaving weirdly in the last couple of days, you might want to check if for spyware, ransomware and other kinds of malware. According to Trend Micro, some high profile websites have been unintentionally exposing their visitors to the Angler exploit kit through some malicious ads. Since this all has happened very recently and the websites don't seem to be at fault, I will not reveal any of their names because I don't want to damage their reputation.
In case you're not a tech-savvy person, I will try to explain what happened as simply as possible. Websites get their ads from some online advertising services, then inject them into their pages. A domain called "brentsmedia.com", which was once a legitimate business used for online advertising has been infected with ads containing an updated version of the Angler exploit kit. Since the source appeared to be a valid one, the infected ads have been injected into some high profile news, entertainment, political commentary websites, thus reaching tens of thousands of unsuspecting victims.
If you've never heard about the Angler exploit kit, it's a nasty hacker's tool that searches the victim's PC for known vulnerabilities and exploits the ones that it finds. In case it finds the necessary entry points, the kit deploys a backdoor dubbed BBEP that allows the attacker to install additional malware or in some cases a type of ransomware called TeslaCrypt. As far as I know, most of the websites in question have already dealt with the problem, but the threat is still out there, so be careful what you click on while you're browsing the Internet.
If you're interested in more security-related stories, you might enjoy reading some of our previous articles like: "What is ransomware and how to protect yourself against it" or "How to know if your PC is part of a botnet".