Do not trust websites promoting the "Mac OS Alert" scam

Also Known As: Mac OS Alert pop-up
Type: Mac Virus
Damage level: Medium

What is the "Mac OS Alert" scam?

"Mac OS Alert" is a scam promoted on various deceptive websites. This scheme claims that visitors' devices may be infected and recommends a quick scan. The fake scan then details several nonexistent viruses and states that the anti-virus suite must be updated. No web page can detect threats/issues present on systems, and any that make such claims are scams.

Schemes of this kind promote various untrusted or even dangerous software. These scams commonly promote potentially unwanted applications (PUAs) such as fake anti-virus programs, adware, browser hijackers, etc. In some cases, they even proliferate malware (e.g. Trojans, ransomware, etc.).

Few users access these deceptive sites intentionally - most access them via mistyped URLs, redirects caused by intrusive advertisements or PUAs.

Mac OS Alert scam

When a website running the "Mac OS Alert" scam is accessed, it displays several pop-up windows. The foremost pop-up informs visitors that their Macs may be infected. To detect the supposed viruses, the scam advises users to scan their devices. The fake scan will take 10 seconds.

To perform the scan and continue, visitors are instructed to click "OK" to continue. Once this window is closed, the background pop-up states that users' devices are supposedly infected with five viruses. Immediate action is required - the anti-virus software must be updated.

Visitors are urged to update their anti-virus suites by clicking "Proceed", followed by "Download" on the next page to install the latest updates. Note that all of the information provided by "Mac OS Alert" is false. I.e., the threats detected by this scheme are fake and merely used as bait to trick users into downloading/installing and/or purchasing the promoted products.

To summarize, by trusting the "Mac OS Alert" scam, users can experience system infections, serious privacy issues, financial loss and even identity theft. Scams like "Mac OS Alert" typically promote various PUAs. These applications often seem legitimate and harmless, and might even be disguised as genuine existing products.

Fake anti-virus tools are amongst the most popular apps endorsed in this fashion. Bogus anti-virus programs require activation (i.e. purchase) to perform the advertised functions, yet even after activation, they remain nonoperational. Some PUAs can force-open bogus, deceptive and malicious sites.

Adware-types run intrusive advertisement campaigns, delivering various pop-ups, banners, coupons and other ads. These diminish the browsing experience, as they overlay page content and reduce browsing speed. Once clicked, intrusive ads redirect to dangerous websites and some can even stealthily download/install software.

Other PUAs called browser hijackers make modifications to browser settings to promote fake search engines. Thus, each new browser tab/window opened and web search done via the URL bar redirects to the address of the promoted web searcher.

Bogus search engines are seldom able to generate search results, and so they tend to redirect to Google, Yahoo, Bing and other genuine sites. Browser hijackers can also restrict/deny access to the browser settings and/or undo any permitted changes made. Furthermore, most PUAs (regardless of type) can track data.

They monitor browsing activity (URLs visited, pages viewed, search queries typed, etc.) and collect sensitive information extracted from it (IP addresses, geolocations and other details). The gathered data usually contains personally identifiable information. In summary, the presence of unwanted software on devices endangers device integrity and user integrity.

Therefore, you are strongly advised to remove all suspect applications and browser extensions/plug-ins immediately upon detection.

Threat Summary:
Name Mac OS Alert pop-up
Threat Type Phishing, Scam, Mac malware, Mac virus.
Fake Claim Scam claims users' devices are infected and their anti-virus programs are outdated.
Related Domains online-virus-scan[.]best
Detection Names (online-virus-scan[.]best) Netcraft (Malicious), Full List (VirusTotal).
Promoted Unwanted Application Various dubious applications.
Serving IP Address (online-virus-scan[.]best)
Symptoms Your Mac becomes slower than normal, you see unwanted pop-up ads, you are redirected to dubious websites.
Distribution methods Deceptive pop-up ads, free software installers (bundling), fake Flash Player installers, torrent file downloads.
Damage Internet browser tracking (potential privacy issues), display of unwanted ads, redirects to dubious websites, loss of private information.
Malware Removal (Mac)

To eliminate possible malware infections, scan your Mac with legitimate antivirus software. Our security researchers recommend using Combo Cleaner.
▼ Download Combo Cleaner for Mac
To use full-featured product, you have to purchase a license for Combo Cleaner. Limited seven days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.

"Your system is heavily damaged by Two viruses!", "Your Apple iPhone is severely damaged by 19 viruses!", "Your Mac is infected with 5 viruses!" and "Check-apple-for-cleaning" are some examples of other scams similar to "Mac OS Alert". The internet is rife with various deceptive websites - they use different models to trick visitors into trusting them.

Common variants include warnings that the device is infected and/or at risk, alerts that an essential software product is out of date, fake prize giveaways and raffles, "unbelievable" offers and deals, etc. Regardless of what these scams claims, offer, request or demand, the purpose is identical: to generate revenue for the scammers/cyber criminals.

Therefore, you are strongly advised to exercise caution when browsing.

How did potentially unwanted applications install on my computer?

PUAs are often downloaded/installed together with other products. This deceptive marketing technique of pre-packing regular software with unwanted or malicious additions is called "bundling".

By rushing through download/installation of software (e.g. ignoring terms, skipping steps and sections, using "Quick/Express" settings, etc.) many users risk unintentionally allowing bundled content into their devices. Intrusive advertisements proliferate PUAs as well.

When clicked, the ads can execute scripts to download/install these applications without users' permission. Some PUAs have "official" download web pages from which they can be downloaded.

How to avoid installation of potentially unwanted applications

You are advised to research all software before download/installation. Use only official and verified download channels. Unofficial and free file-hosting websites, Peer-to-Peer sharing networks (BitTorrent, Gnutella, eMule), and other third party downloaders commonly offer harmful and bundled content, and are therefore untrusted and should be avoided.

When downloading/installing, read the terms, study all possible options, use the "Custom/Advanced" settings and opt-out of additional apps, tools, features, and so on. Intrusive advertisements typically seem legitimate, however, they can redirect to dubious and malicious sites (e.g. gambling, pornography, adult-dating, and many others).

If you encounter ads or redirects of this kind, inspect the system and remove all dubious applications and browser extensions/plug-ins immediately. If your computer is already infected with PUAs, we recommend running a scan with Combo Cleaner Antivirus for macOS to automatically eliminate them.

Screenshot of a browser notification promoting the "Mac OS Alert" scam:

Notification promoting Mac OS Alert scam

Appearance of "Mac OS Alert" scam (GIF):

Appearance of Mac OS Alert scam (GIF)

Instant automatic Mac malware removal: Manual threat removal might be a lengthy and complicated process that requires advanced IT skills. Combo Cleaner is a professional automatic malware removal tool that is recommended to get rid of Mac malware. Download it by clicking the button below:
▼ DOWNLOAD Combo Cleaner for Mac By downloading any software listed on this website you agree to our Privacy Policy and Terms of Use. To use full-featured product, you have to purchase a license for Combo Cleaner. Limited seven days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.

Quick menu:

How to identify a pop-up scam?

Pop-up windows with various fake messages are a common type of lures cybercriminals use. They collect sensitive personal data, trick Internet users into calling fake tech support numbers, subscribe to useless online services, invest in shady cryptocurrency schemes, etc.

While in the majority of cases these pop-ups don't infect users' devices with malware, they can cause direct monetary loss or could result in identity theft.

Cybercriminals strive to create their rogue pop-up windows to look trustworthy, however, scams typically have the following characteristics:

  • Spelling mistakes and non-professional images - Closely inspect the information displayed in a pop-up. Spelling mistakes and unprofessional images could be a sign of a scam.
  • Sense of urgency - Countdown timer with a couple of minutes on it, asking you to enter your personal information or subscribe to some online service.
  • Statements that you won something - If you haven't participated in a lottery, online competition, etc., and you see a pop-up window stating that you won.
  • Computer or mobile device scan - A pop-up window that scans your device and informs of detected issues - is undoubtedly a scam; webpages cannot perform such actions.
  • Exclusivity - Pop-up windows stating that only you are given secret access to a financial scheme that can quickly make you rich.

Example of a pop-up scam:

Example of a pop-up scam

How do pop-up scams work?

Cybercriminals and deceptive marketers usually use various advertising networks, search engine poisoning techniques, and shady websites to generate traffic to their pop-ups. Users land on their online lures after clicking on fake download buttons, using a torrent website, or simply clicking on an Internet search engine result.

Based on users' location and device information, they are presented with a scam pop-up. Lures presented in such pop-ups range from get-rich-quick schemes to fake virus scans.

How to remove fake pop-ups?

In most cases, pop-up scams do not infect users' devices with malware. If you encountered a scam pop-up, simply closing it should be enough. In some cases scam, pop-ups may be hard to close; in such cases - close your Internet browser and restart it.

In extremely rare cases, you might need to reset your Internet browser. For this, use our instructions explaining how to reset Internet browser settings.

How to prevent fake pop-ups?

To prevent seeing pop-up scams, you should visit only reputable websites. Torrent, Crack, free online movie streaming, YouTube video download, and other websites of similar reputation commonly redirect Internet users to pop-up scams.

To minimize the risk of encountering pop-up scams, you should keep your Internet browsers up-to-date and use reputable anti-malware application. For this purpose, we recommend Combo Cleaner Antivirus for macOS.

What to do if you fell for a pop-up scam?

This depends on the type of scam that you fell for. Most commonly, pop-up scams try to trick users into sending money, giving away personal information, or giving access to one's device.

  • If you sent money to scammers: You should contact your financial institution and explain that you were scammed. If informed promptly, there's a chance to get your money back.
  • If you gave away your personal information: You should change your passwords and enable two-factor authentication in all online services that you use. Visit Federal Trade Commission to report identity theft and get personalized recovery steps.
  • If you let scammers connect to your device: You should scan your computer with reputable anti-malware (we recommend Combo Cleaner Antivirus for macOS) - cyber criminals could have planted trojans, keyloggers, and other malware, don't use your computer until removing possible threats.
  • Help other Internet users: report Internet scams to Federal Trade Commission.

▼ Show Discussion

About the author:

Tomas Meskauskas

Tomas Meskauskas - expert security researcher, professional malware analyst.

I am passionate about computer security and technology. I have an experience of over 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an author and editor for pcrisk.com since 2010. Follow me on Twitter and LinkedIn to stay informed about the latest online security threats. Contact Tomas Meskauskas.

PCrisk security portal is brought by a company RCS LT. Joined forces of security researchers help educate computer users about the latest online security threats. More information about the company RCS LT.

Our malware removal guides are free. However, if you want to support us you can send us a donation.

About PCrisk

PCrisk is a cyber security portal, informing Internet users about the latest digital threats. Our content is provided by security experts and professional malware researchers. Read more about us.

Removal Instructions in other languages
Malware activity

Global malware activity level today:

Medium threat activity

Increased attack rate of infections detected within the last 24 hours.

QR Code
Mac OS Alert pop-up QR code
Scan this QR code to have an easy access removal guide of Mac OS Alert pop-up on your mobile device.
We Recommend:

Get rid of Mac malware infections today:

Download Combo Cleaner for Mac

Platform: macOS

Editors' Rating for Combo Cleaner:
Editors ratingOutstanding!

[Back to Top]

To use full-featured product, you have to purchase a license for Combo Cleaner. Limited seven days free trial available. Combo Cleaner is owned and operated by Rcs Lt, the parent company of PCRisk.com read more.