Security Master: Antivirus, VPN, AppLock, Booster review

Clean, maintain and secure your Android device

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Our Verdict

Underpowered in some areas, but the reliable antivirus and versatile app locker won us over.


  • Free version
  • Loads of features
  • Highly-rated antivirus
  • Powerful application locker


  • Some misleading ads
  • Very basic VPN
  • Underpowered 'booster' tools
  • Expensive Premium plan

Security Master: Antivirus, VPN, AppLock, Booster is Cheetah Mobile's one-stop security, maintenance and optimization app for Android. 

The antivirus module does an unusually good job of scanning your device for malicious apps. No need to take our word for it; the January 2018 AV-Test report found Security Master blocked 100% of test threats . 

A custom browser blocks ads while antiphishing protection prevents you accessing malicious URLs, keeping many web threats at bay. 

A simple VPN encrypts your network activity, gives you a new virtual location and perhaps helping to access blocked websites. It's based on Hotspot Shield Free VPN Proxy so there's not much power or configurability under the hood, but the service is still a welcome inclusion in the package. 

The AppLock feature enables protecting any or all of your apps with a pattern, a PIN or (on some devices) a fingerprint, keeping snoopers firmly locked out. If someone tries to get in anyway but fails, you can have Security Master take a photo of the intruder and email it to you. 

Booster modules claim to optimise your device by deleting junk files, clearing away useless notifications, keeping your CPU cool and extending your battery life.

Learning how to operate all of this could have been difficult, but fortunately it isn't necessary: you can have Security Master scan your system to make its main recommendations, then apply them all in a couple of taps. 

Security Master's core features (just about everything but the VPN) are available in an ad-sponsored free version. 

The Standard version drops the ads, enables automated device boosting for better performance and provides a daily 200MB VPN data allowance for £2.49 ($3.49) a month, or an equivalent £0.83 (£1.16) a month if you pay for a year up-front. 

The Premium edition supports unlimited VPN use for a costly £10.99 ($15.39) a month, dropping to £2.87 ($4.02) for the first year on the annual plan. 

Security Master on Google Play


Security Master is simple to set up, with no registration or other issues involved-- we just tapped Install from the Google Play store and the app was ready to go within a few seconds. 

The app interface can seem complicated, as there's a lot going on. A Scan button enables checking everything; there are separate icons to run the Antivirus, AppLock, Clean Junk, CPU Cooler, Notification Cleaner and Phone Boost features, and below that is a mix of status information (battery life, the wifi network you're currently accessing) and shortcuts to yet more app modules (Game Boost, Message Security, Safe Browsing, SafeConnect VPN). 

The Scan function checks your device for malicious apps, malware, poorly configured settings and more. The reporting isn't always clear - the app told us it had found a virus, but not what or where that was - but it's undeniably easy to use. 

The AppLock module displayed our installed apps and made intelligent recommendations about the apps to protect (Messenger, Photos, Chrome.) We accepted its advice and were prompted to choose a PIN that would unlock all three apps (you can't have a per-app unlock method). 

After the initial setup Security Master displayed our locked apps, made further suggestions about others, and enabled locking or unlocking any app with a tap. 

We found Security Master correctly stepped in to restrict access to our selected apps, allowing us in when we entered our PIN. This should be easy enough to remember as there's only one, but Security Master also allows users to specify a security question (what's your favourite movie, mother's name, father's name, where did you go to school, and so on) which enables resetting the PIN later if you forget it. 

The Junk File tool found 438MB of leftover data which could be safely deleted. That wasn't bad for a relatively clean device, but when we ran CCleaner for a comparison it found 702MB of junk. 

A CPU Cooler option displays your device temperature and lists any apps using CPU resources. There's also a Fix button, although that doesn't seem to do anything other than close the offending apps. 

The Battery Saver has a similarly basic approach, analysing power use and recommending that you hibernate the most power-hungry apps. It doesn't appear to be very different to the myriad of similar apps, but should still help to improve your battery life. 

The Notification Cleaner says it will remove trash notifications, but there's no information on how it decides what to remove, and no control over what happens (you can't say 'remove this but keep that'.) 

The Phone Booster also offers no real control or feedback. We ran it, were told our memory was 77% used before, 64% afterwards, and that was it. There was no indication of which app was consuming most RAM or what had been tweaked to reduce its requirements. 

A follow-up screen offered some useful extras, including a performance test which reported on our connection's upload and download speed. These were handy, but difficult to access. When we tapped Phone Booster later, it didn't display the bonus tools, instead simply showing us an ad and returning us to the main screen. 

A Game Booster may also try to free up RAM, although there's no clear explanation of what it's doing. Its main benefit is that you're able to set up a shortcut to automatically run the Booster when the game is launched. 

The SafeConnect VPN connected us quickly to a local UK server. Speeds were very inconsistent, though, sometimes ranging from 500Kbps to 17Mbps during the same test. The 200MB daily allowance is also too limited to be of much use, and upgrading to the Premium edition to get unlimited VPN is too expensive. You can get unlimited VPN elsewhere for free, or subscribing to a specialist VPN provider would get you a better quality of service which you could use on more devices. 

Finally, a Safe Browsing feature combines some of the other tools to lock your browser screen, encrypt your internet connection via a VPN and clear your browsing history after a session. We suspect Chrome's incognito mode would deliver the core privacy you need and be much simpler to use, but the feature may still be useful to some. 

The free version of Security Master comes with plenty of ads, in many different types: embedded images, full screen, multiple styles of close button, sometimes with a timer. They're annoying, but no more so than with the average ad-sponsored app.

One problem we did notice was a series of ads clearly designed to deceive you. These looked similar to the web popups you'll sometimes get on dubious sites, where a window appears telling you 'You're infected by a virus, click Install to fix it!' You can (and should) ignore them, but at a quick glance it's not always obvious that they're ads, and it's easy to imagine how someone might panic and click Install without thinking. 

These ads aren't controlled by Cheetah Mobile, and installing the advertised apps probably won't harm your device, anyway, but this still has to be a concern. Security Master is supposed to help protect your system, not provide a new way for dishonest developers to trick you into installing their products. 

Security Master app


Many Android security apps make big claims about their malware-scanning abilities, but without any supporting evidence. Security Master is different, fortunately-- it's been around for a long time and has been tested by the main independent testing labs. 

AV-Test's January 2018 Android report found Security Master blocked 100% of its test samples (that's more than 2,700). The app managed the same perfect rating in the previous two tests (September and November 2017). 

AV-Test was less convinced by the range of features available, though. The app was marked down for its lack of message and email filtering, parental controls or backup functions. 

AV Comparatives' January 2018 Android report gave test results for more than 200 Android security apps. With the default settings Security Master managed a slightly below average 96.4% protection score, but the report notes that if users turn on the Anti-heuristic detection engine (disabled by default in the English/ International version) then it would block 100% of threats. 

These tests didn't assess Security Master's URL blocking feature, so we ran some small-scale checks of our own. It kept us safe from 70% of newly reported malicious links in our test sample, an above-average result. 

Factor in Security Master's device protection tools - in particular, AppLock - and the app generally does a good job of keeping your device (and data) safe from harm. 

Final verdict

Security Master is a bulky suite with some very average tools, but the antivirus is accurate and the app locker is also worth having. Give it a try, but watch out for deceptive ads.