Windows 8 Defender Rated Worst Antivirus For Protection

Windows 8 Defender is the worst rated antivirus product for Protection (of 25 tested), according to new research from independent test lab AV-Test. Defender is Microsoft’s free antivirus product, enabled by default in Windows 8. It is very similar to the popular Microsoft Security Essentials (MSE) – it uses the same anti-malware engine and looks almost identical.

As Defender is so similar to MSE, last October I reviewed how MSE compared to other antivirus products – it was the only one of 24 products tested not to achieve AV-Test certification and was bottom of the pile for Protection, scoring just a quarter of the top product rating.

However, some readers claimed that as these tests were of a different product (MSE) running on Windows 7, they could not be representative of Defender on Windows 8, however similar they were. Today’s new research provides better evidence as it tests Defender itself against other products, on Windows 8 – we no longer have to infer its performance by comparing with MSE.

So how did Windows 8 Defender do? As we expected, very poorly – it was joint bottom for Protection. Perhaps slightly more surprising is that Defender’s score for Performance (average influence on the computer’s speed) was in the bottom half of the results too – users clinging onto Defender because MSE had a reputation for being quick and lightweight should take note.

AV-Test results for Protection show that Defender scored 2 out of 6 – compared to 5.5 for leading free rivals Avast and AVG:


But what do those scores mean in practice? Digging deeper reveals the following details for the tests:

Zero-Day malware, real world testing – This is the toughest test because the malware is new and so is not already included in the security product’s malware definitions – industry average detection rates are 95%.

  • Defender detected just 82% of samples in Jan and 81% in Feb whilst Avast and AVG both detected 98% and 100% respectively – a huge difference which accounts for the poor Defender score.

These results clearly show that Defender (like its twin MSE) struggles to detect new malware and highlights the additional security that better free products provide. The best paid products provide only a minor improvement – the top rated BitDefender IS detected 100% of zero day malware in both months.

Despite these results, MSE (and, by association) Defender is increasingly popular – a recent study by Opswat revealed that MSE is far and away the number one AV in North America with a huge 30% share of the market – a 9% increase over the last 6 months.

Perhaps the simplicity of MSE/Defender (a ‘set and forget’ antivirus product) has struck a chord – or else many users rather naively trust Microsoft to produce good security software for Windows…


Windows 8 Defender (like MSE) is very easy to use and requires no configuration. However, it is no longer as lightweight/quick as before and protection against more recent malware, especially 0-day threats, is very poor in comparison to other products tested.

It is also worth noting that both its main free rivals provided almost as much Protection against malware as the very best paid products.

[Source: AV-Test Jan/Feb 2013 Windows 8 Test Report]