I’ve been curious about this, so I’ve done some tests. There have been a couple surprises. I’ve tested 10 antivirus programs for resource usage while scanning and at idle. Detection rates have not been tested as I’m not in the habit of keeping a lot of viruses around and am more concerned with what the program is like to live with. It can be assumed that all these widely used products offer fairly good detection.

The testing was done on a virtual machine running Windows 7 32-bit with 1GB of RAM and one 2.0Ghz CPU. The OS was prepared along with this guide to ensure it wasn’t doing much apart from running the OS and the AV program.  The VM was reset to its original snapshot before each test.

The tests were conducted as follows:

Download and install the antivirus program, start a scan, check memory and CPU usage. Restart the virtual machine, wait about 5mins and see what the memory and CPU usage was like at idle. This isn’t a 100% reliable method but there’s enough to draw comparisons.

The software will be compared on:

• Memory and CPU usage behaviour while scanning
• Memory and CPU usage behaviour while at idle
• Ease of installation and use, any detractors (drive-by installs, unwanted toolbars, pestering etc)

The main focus is free antivirus products, but two paid products are included for comparison. I’ve selected Trend Micro – one I usually don’t like, and NOD32 – one I use. If I can save a couple people some time choosing an AV, I’ll be happy.

On with the test. If you just want to read the conclusion, go for a scroll to the bottom.

The baseline

With no resident antivirus, memory usage was pretty steady at a hair under 270MB and the CPU wasn’t terribly busy with no large spikes.

Ad-Aware Internet Security

The user interface doesn’t instill a lot of confidence with this one, as it looks very amateur. It didn’t take too long to install and downloaded about 90MB of definition files afterwards at a decent speed. It took 12mins from clicking the download link to starting the first scan.

While scanning

CPU: Basically solid at 100% CPU utilization
System memory usage: Set in stone at 530MB

At Idle

CPU: Some odd spikes to 100% utilization can be seen

System memory usage: 401MB – pretty high

avast! Free Antivirus

10mins from clicking the download link to starting the first scan. No significant complaints really, the UI looks a little busy and takes up a lot of screen space. The tray icon does a regular rotating animation which can be distracting.

While scanning

CPU: Only momentarily hit 100% a couple times, seems to avoid overutilisation, spending a lot of time around 60%.

System memory usage: 466MB

At Idle

CPU: Not much to see here, one spike.

System memory: Only 279MB.

AVG Antivirus Free Edition 2012

Took 20mins from starting the download to starting a scan. A very long time was spent downloading definitions. I’ve seen a lot of comment that later versions of AVG are bloated and heavy, I suspect they have reversed this trend with the current version.

While scanning

CPU: High, 80-90% most of the time, seemed to “bounce off” 100 though.

System memory: Low at only 352MB (50MB less than Ad Aware while idle…)

At Idle

CPU: Three spikes.

System memory: 279MB, very good.

Avira Free Antivirus

Another long install process. Some odd behaviour from the UI when first opened. Luke Filewalker.

While scanning

CPU: On the high side, though seemed to settle down. I suspect it depends on what is being scanned.

System memory: 572MB

At Idle

CPU: 4 spikes

System memory: 308MB, not bad.

Comodo Internet Security Premium

A couple gripes, 22 minutes until I could do a scan and I ended up with a program called Comodo GeekBuddy which is some kind of paid support chat client complete with tray icon that required an update be downloaded immediately after installation. It wasn’t optional during the install. It does however include a firewall.

While scanning

CPU: A lot of time at 100%

System memory: Steady at just under 450MB

At Idle

CPU: Some spikes. Was it the antivirus, or the firewall or geekbuddy?

System memory: 448MB

Microsoft Security Essentials

It’s Microsoft, so that counts for something. Security Essentials and Live One Care before it were acquired from a 3rd party and not developed in house. One big positive is it was only 5mins to download, install and start the first scan which is way ahead of anything else here.

While scanning

CPU: Generally over 90%

System memory: Lean at 359MB

At idle

CPU: Very busy beyond 5mins from boot. Not sure what’s going on but it probably isn’t good.

System memory: 366MB – more than during the scan?

Panda Cloud Antivirus Free

Light as a feather they say. Has been recommended for netbooks. Reasonably painless installer taking 9mins until the scan could be done. “Neutralized” a cookie during the scan. Cute icon. Negative points for B.S. in regards to lightness and cloud benefits as shown below.

While scanning

CPU: A lot of time at 100%

System memory: 498MB

At Idle

CPU: 2 Big spikes, 3 little ones.

System memory: 308MB. Good but this program is no lighter than others without “Cloud” in the name.

PC Tools Antivirus Free

This is the only antivirus program here that I would recommend avoiding if you’re looking for “light”. The issues with this one started with the installer. After downloading itself and some definitions, it then proceeded to download another 150MB of definitions which is almost double the size of the definition files the rest of these are using. Does it detect twice as many viruses? Unlikely. It also managed to detect a number of cookie “infections” during the scan. Please people, cookies are not malware.

While scanning

CPU: High but stayed away from 100% which was good.

System memory: 724MB, the most of anything tested.

At Idle

CPU: PC Tools really went to town on the CPU while idle. I’ve included a few extra screenshots through to 8mins in this case.

System memory: 348-422MB during minutes 5 through 8.

Paid Products

Here’s a couple that aren’t free for comparison. I’ve chosen one I’ve never been too fond of, Trend Micro and the one I currently use, ESET NOD32.

NOD32 5

NOD32 has been the long term king of speed and efficiency. Looks like there’s a pretty good opportunity to knock if off its perch at the moment as the results were good, but didn’t show the leadership margin I was expecting. It was also difficult to test as a trial install was used initially but without registering an e-mail address on it, NOD32 would repeatedly attempt updates on idle and fail causing CPU usage spikes. Once this was done it dropped back to a low level of resource usage.

While scanning

CPU: Fairly high staying over 80%

System memory: 425MB

At Idle:

CPU: Sustained high usage around the 5min mark then dropped to practically nothing beyond that.

System memory: 292MB not the lowest but fairly low.

Trend Micro Titanium

Despite the impressive name, this is strictly an antivirus/antispyware program and didn’t include a firewall like most internet security suites. I expected performance to be terrible since dealing with past Trend Micro AV products. I was wrong. One interesting thing was a “Preparing to configure windows” screen upon restarting. This one may use some kind of driver architecture that can’t be installed while windows is running.

While scanning

CPU: Up and down with a lot of time sustained at 100%

System memory: 521MB

At Idle

CPU: A couple spikes but pretty good.

System Memory: 367MB during the 5minute point the screenshots were usually taken, however this dropped to 301MB later on which was a positive development.

Results ranked by CPU usage while scanning:

1. Avast
2. Avira
3. PC Tools
4. NOD32
5. Trend Micro
6. AVG
7. Panda
8. Microsoft
9. Comodo
10. Ad-Aware

Results ranked by system memory usage while scanning:

1. AVG (352)
2. Microsoft (359)
3. NOD32 (425)
4. Comodo (450)
5. Avast (466)
6. Panda (498)
7. Trend Micro (521)
8. Ad-Aware (530)
9. Avira (572)
10. PC Tools (724)

Results ranked by CPU usage while idle:

1. Avast
2. Comodo
3. Panda
4. Trend Micro
5. Ad-Aware
6. AVG
7. Avira
8. NOD32
9. Microsoft
10. PC Tools

Results ranked by system memory usage while idle:

1. Avast (279)
1. AVG (279)
3. NOD32 (292)
4. Panda (308)
5. PC Tools (348)
6. Microsoft (366)
7. Trend Micro (367)
8. Ad-Aware (410)
9. Comodo (448)
10. Avira (572)

Conclusion

This one definitely goes to Avast, seeing as resource usage was low across the board, particularly while acting in a real-time/resident capacity which is going to have the most impact on PC performance overall. Only detractor on this one was the tray icon animations, but I’d just hide that.

AVG also performed very well dispelling any suspicion regarding bloat. Matching avast in one instance. I’d still call it light.

Products one should steer clear of, if performance is a priority, were Avira, PC Tools and Ad-Aware which were all pretty awful. Comodo takes the cake for installing unwanted software and a long install process but performance was not poor, merely average after that. It also needs to be taken into account that Comodo was running a firewall as well.

Paid products: NOD32 performed comparatively worse than I would expect it to, but still fairly well. Hopefully ESET will focus more on performance for Version 6.0, though this may be solvable with point release updates for version 5. Trend Micro did much better than I expected, keeping it a viable option, but it still ranked behind NOD32.