Not legitimate. Firefox does not do malware scans. That display is probably malware that you have picked up somewhere. Some malware disguises itself as legitimate anti-malware programs.

See this first. Look at Post #2 and Post #3 and follow the instructions: http://forums.malwarebytes.org/index.php?showtopic=38629&st=0&p=193287&#entry193287

Do a thorough scan for other malware Install, update and run these programs in this order. They are all free for personal use, but some have limited functionality in the "free mode", but those are features you really don't need to find and remove the problem that you have. (Not all programs detect the same Malware.)

Malwarebytes' Anti-Malware - http://www.malwarebytes.org/mbam.php SuperAntispyware - http://www.superantispyware.com/ AdAware - http://www.lavasoftusa.com/software/adaware/ Spybot Search & Destroy - http://www.safer-networking.org/en/index.html Windows Defender - http://www.microsoft.com/windows/products/winfamily/defender/default.mspx Dr. Web Cureit - http://www.freedrweb.com/cureit/

If these don't find it or can't clear it, post in one of these forums for specialized malware removal help: http://www.spywarewarrior.com/index.php http://forum.aumha.org/ http://www.spywareinfoforum.com/ http://bleepingcomputer.com

I had a similar issue... I was browsing the web and opened a web page. My computer appeared to freak out... sending legitimate looking alerts and messages that I was infected with multiple viruses. It took me a minute to realize that these messages were coming from the internet and NOT from my virus protection (McAfee).

If my antivirus is up to date, and I did not click any of the pop-ups, do I still need to follow the advice previously posted? I'm doing a full scan of my system with McAfee, just to be on the safe side.

In some cases, the fake anti-virus will install malware if you click on a "Close" button or the "X" on the fake alert window. Generally, close in Task Manager's Processes tab, IF you can recognize the correct process to terminate.

Yes, do a complete, thorough malware scan.

In addition to the other replies I would suggest that before doing anything, don't panic: press Ctrl - Alt (simultaneously) and then while holding these keys down press Delete. this will take you out of the program and/or website where you can then do a re-boot. Immediately after the re-boot do your antivirus scans etc.