The Best Free Antivirus for Windows – January 2016

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I have been looking into the question of which free antivirus is the best for almost 10 years now, and the only way to answer is by looking at comparative tests with hard data, keeping in mind that the programs themselves are constantly changing and being updated, and that the picture that emerged from last year’s tests, say, may have changed with the more up-to-date round of tests, etc.

We will turn to “av-comparatives.org” for our data, since they regularly run what are arguably the web’s best and most comprehensive antivirus tests. As I write this in Jan 2016 I will use the latest versions of their tests, conducted within the last 6 months of this writing.

The contenders: a scan of several of the tests they conducted reveals a clear picture of who the ‘real’ players are. For free antivirus programs, the top three are Avira, AVG, and Avast. (Note: I debated whether to include Panda free antivirus, which seems like it wants to be a contender, but decided to skip it as it is clearly ‘not there yet’). In order to provide a frame of reference, I will also include the test results of the top three paid antivirus programs, which can also be identified with a cursory inspection of the results: Kaspersky, BitDefender, and Eset. I will also copy the practice from av-comparatives, of considering Microsoft Security Essentials as a control, the idea being that since it is now provided pre-intalled with on many Windows PC’s, you would need to install another antivirus program in it’s place only if it is the case that this new program provides significant additional protection.

The question I am looking answer:  simply, what is the best free antivirus program, and how does it fare compared to the paid programs.

The evaluation criteria: generally speaking, the three things I cared about were (1) The detection rate: i.e. how likely it is to catch viruses, (2) Performance: i.e. how much of the system resources did it drain; and (3) The rate of false positives: i.e. how likely it is to ‘catch’ things that it shouldn’t. All of this info was available in the av-comparatives data, although the tests didn’t necessarily correspond one-to-one with my criteria and other variables were also involved.

The tests that we looked at: we as a rule, and because we were writing this in January 2016, we only wanted to look at tests conducted within the last 6 months of 2015 (there were no tests conducted in 2106).

Also, because this is an investigation into the best free antivirus, we excluded any test that did not include all three free antivirus programs (Avira, AVG, and Avast).

Therefore, we looked at the following tests. Only the ones below fit our criteria

  1. Real-World Protection Test August – November 2015
  2. Performance – Test October 2015
  3. File Detection and False Positives Test – September 2015

Below, we will look at each one of these tests in turn. Note that we are using a color coding system in the tables as follows:  Green=Hight/Best ,  Orange=Middle , and   Red=Low .

1. Real World Protection Test (AUG-NOV 2015)

In this test, each antivirus program had it’s own dedicated machine which was connected to the internet and was interacting with hundreds of URLs each day.  It was automated (rather than carried out by human subjects). All the antivirus programs were being updated on the morning of every day. The methodology of this test is quite interesting, actually, so make sure to read the original description of it in the downloadable PDF, which you can find via the av-comparatives website on this page.

In a nutshell, this is testing ‘in the field’, like a poll designed to measure the degree of protection these antivirus programs would offer in the real world over a long period (5 months) — as opposed to an artificial test where the programs are subjected to ‘canned’ threats. The results are in the table below:

Real World Protection Test: average from AUG - NOV 2015
Free Programs Paid ProgramsControl
AvastAVGAviraBitdefenderESETKasperskyMicrosoft
Protection Rate (1)98.8%99.3%99.9%99.9%98.7%99.9%94.5%
Wrongly blocked
domains & files (2)
60632029
AV Comparatives
Award level (3)
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Standard
1 star
(1) Higher is better. The average real world protection rate for all was 97.53%. (2) Lower is better. The average wrongly blocked domains and files for all programs tested was 15. (3) AV Comparatives suggest that products with the same award be considered equivalent in their real world protection effectiveness.

 

Interpretation: what we can conclude from the “Real World Protection Test AUG – NOV 2015”:

  1. The three best free Antivirus programs (Avira, AVG, and Avast) and the three best paid ones (Kaspersky, BitDefender and ESET) are all comparable in their protection rate and the rate of wrongly blocked domains and files, in a real world test over five months, despite minuscule yet ultimately insignificant variations.
  2. The six programs above are all significantly better than the control (Microsoft Security Essentials).

 

2. Performance Test (OCT 2015)

A test designed to measure the extent to which the antivirus program uses up system resources and/or contributes to slowing down your system, especially during tasks that antivirus software typically monitors. Each program was running on its own dedicated PC and a benchmarking app PC Mark 8 Professional used to measure system performance. The tasks involved in the test were: file copying, archiving and archiving, installing and uninstalling applications, launching applications, and downloading files.

If you’d like to know more about this test, you can download the detailed PDF from this page. The results are displayed in the table below:

Performance Test: OCT 2015
Free Programs Paid ProgramsControl
AvastAVGAviraBitdefenderESETKasperskyMicrosoft
System Impact Score (4)2.77.22.37.57.75.416.2
AV Comparatives
Award level (5)
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced
2 stars
(4) Lower is better. The average system impact score  in this test was 13.07.  (5) AV Comparatives suggest that products with the same award be considered equivalent in their system resource usage.

 

Interpretation: what we can conclude from the “Performance Test Oct 2015” test:

  1. The three best free Antivirus programs (Avira, AVG, and Avast) and the three best paid ones (Kaspersky, BitDefender and ESET) are all comparable in the degree that they impact the system or use up resources, despite minuscule (yet ultimately insignificant) variations.
  2. The six programs above are all significantly better than the control (Microsoft Security Essentials), in terms of resource usage.
  3. The three free programs are generally lighter than the paid programs, with Avira and Avast taxing the system least of all, although not significantly so.

 

3. File Detection and False Positives Test – (September 2015)

This is a more typical test that the ‘real world’ test above, in that products were essentially subjected to a collection of malware (166522 malware samples), and the detection rate measured. Note that the real world test is probably more relevant to real world users who get exposed to malware from the internet; however, this one is a good test for detection of malware that might come from sources other than the internet or for the best antivirus options to use on an already infected system.

If you’d like to know more about this test, you can download the detailed PDF from this page. The results are displayed in the table below:

Malicious File Detection and False Positives Test: SEP 2015
Free Programs Paid ProgramsControl
AvastAVGAviraBitdefenderESETKasperskyMicrosoft
Detection Rate (6)99.2%93.4%99.8%99.8%99.2%99.5%91.4%
False Positives (7)35642020
AV Comparatives
Award level (8)
Advanced
2 stars
Standard
1 star
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Tested
No star
(6) Higher is better. The average detection rate for all in this test was xx.xx%. (7) Lower is better. The average for programs tested was 15. (8) AV Comparatives suggest that products with the same award be considered equivalent in their correct detection rates.

 

Interpretation: what we can conclude from the “File Detection and False Positives Test – (September 2015)” test:

  • All the paid programs did really well on this test and had high detection rates and low false positives.
  • As for the free options: Avira is a cut above the rest, comparable to the paid programs. AVG had a comparatively poor detection rate, while the good detection rate for Avast was dragged down by a very high rate of false positive.
  • The six programs above are all significantly better than the control (Microsoft Security Essentials), in terms of detection rate.
  • However, be mindful that this is a test within an artificial environment that does not exist in the real world. Users in the real world will experience the kind of protection illustrated in test #1 above.

 

The Verdict: 

Summary of Tests
Free Programs Paid ProgramsControl
AvastAVGAviraBitdefenderESETKasperskyMicrosoft
1. Real World Protection
Test AUG – NOV 2015
WEIGHT=50%
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Standard
1 star
2. Performance Test:
OCT 2015
WEIGHT=35%
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced
2 stars
3. Malicious File
Detection & False
Positives Test: SEP 2015
WEIGHT=15%
Advanced
2 stars
Standard
1 star
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Advanced +
3 stars
Tested
No star

Please note: don’t average results for all three tests. Test #1 would weigh 50% in my estimation, followed by 35% weight for test #2, and only 15% for test #3.

Interpretation: to summarize the overall picture

  • It is possible to conclude: all of the 6 antivirus programs mentioned here are essentially excellent, as evidenced by test #1. Also, all of them beat the control significantly (Microsoft Security Essentials)
  • If you insist on finding a champion”best free antivirus”, then Avira is it, providing high detection rates across the board with low false positives, and is lightest on the system’s resources to boot (even when compared to ALL the programs mentioned in this post, free or paid).
  • Avast would be the second best free option, adversely impacted only by a (possible) high rate of false positives, and AVG could be ranked a very close third (the reason: a lower relative detection rate when artificially bombarded with canned malware).
  • Having said the above, I will repeat: the differences between the free options might well be negligible. If you like any one of the three, are used to it, or just happen to have it installed on your system — then stick with it.

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