Safari locked with Mac security alert

You may have installed one or more of the common types of ad-injection malware. Follow the instructions on this Apple Support page to remove it. It's been reported that some variants of the "VSearch" malware block access to the page. If that happens, start in safe mode by holding down the shift key at the startup chime, then try again.

Back up all data before making any changes.

One of the steps in the article is to remove malicious Safari extensions. Do the equivalent in the Chrome and Firefox browsers, if you use either of those. If Safari crashes on launch, skip that step and come back to it after you've done everything else.

If you don't find any of the files or extensions listed, or if removing them doesn't stop the ad injection, ask for further instructions.

Make sure you don't repeat the mistake that led you to install the malware. Chances are you got it from an Internet cesspit such as "Softonic," "CNET Download," or "SourceForge." Never visit any of those sites again. You might also have downloaded it from an ad in a page on some other site. The ad would probably have included a large green button labeled "Download" or "Download Now" in white letters. The button is designed to confuse people who intend to download something else on the same page. If you ever download a file that isn't obviously what you expected, delete it immediately.

Malware is also found on websites that traffic in pirated content such as video. If you, or anyone else who uses the computer, visit such sites and follow prompts to install software, you can expect more of the same, and worse, to follow. Never install any software that you downloaded from a bittorrent, or that was downloaded by someone else from an unknown source.

In the Security & Privacy pane of System Preferences, select the General tab. The radio button marked Anywhere should not be selected. If it is, click the lock icon to unlock the settings, then select one of the other buttons. After that, don't ignore a warning that you are about to run or install an application from an unknown developer.

Still in System Preferences, open the App Store or Software Update pane and check the box marked

Install system data files and security updates (OS X 10.10 or later)

or

Download updates automatically (OS X 10.9 or earlier)

if it's not already checked.

In the upper right of the menu bar on your Mac, click the Wi-Fi icon, and click Turn off Wi-Fi. If you are using an Ethernet connection to get online, disconnect the Ethernet cable instead. Now force quit Safari, and restart it normally. The malicious page will still try to load, but it can't without an Internet connection. Close the tab. Reconnect to the Internet.

This just happened to me. I called & guy talked me thru getting back..then wanted to charge $99.99 to fix the problem(he said a virus infection) I could not understand his accent and he hung up finally. I think it was a blessing.

There is a better fix for this:

1. In terminal, type: sudo nano /etc/hosts
2. paste '0.0.0.0 macsecurityservice.info' onto the last line
3. ctrl-x, enter to save the file
4. In terminal, type: sudo dscacheutil -flushcache

The /etc/hosts file should look something like this (assuming you've never edited it): https://gist.github.com/hanleybrand/08ea56c15fc6c9d595ec