Best and Lightest Antivirus Software (reviewed using actual memory usage tests)

One of the most common things users do to try and keep their computer running as smooth as possible, is keep control over which programs start with Windows. Having just a few memory or processor hungry programs loading into the system tray on boot can have an adverse affect on the performance of your computer. One of the most common applications that will load with Windows and stay resident in the background while the system is on, will be your chosen antivirus software. Have you ever wondered which are the lightest antivirus packages available and which ones don’t do so well on memory usage?
It’s maybe not such a major issue for newer computers these days having an antivirus which isn’t especially memory efficient because they often come equipped with 4GB or more of RAM. But if your computer isn’t the latest and greatest, using a package which might possibly be eating hundreds of Megabytes of system memory could slow your computer down considerably at inopportune moments. To find out just how much memory gets used by running antivirus software, we’ve decided to gather together a mixture of 25 popular commercial and free antivirus packages to see how they perform.

How We Tested

As you might expect, testing an antivirus product for its memory usage is certainly not an exact science because the program is never standing still and nearly always doing something in the background. A problem with taking memory readings is there are several different numbers you can look at. The two memory readings we paid most attention to were “Working Set” and “Private Working Set” (WS Private), which do two things:
  • Working Set – This is the amount of memory used by the process PLUS the amount of memory that is shared with other processes. As such, this value isn’t truly accurate because shared memory can be double counted due to the same resource being registered in multiple processes. It does though represent the maximum amount of non virtual memory in use by the process. This is the default memory column in the Windows XP Task Manager.
  • Private Working Set – Is similar to Working Set, but excludes the shared memory. This is only the the amount of memory in use by the process itself and isn’t shared among other processes. Private Working Set is perhaps a more accurate indication of how much physical memory the process itself is using, and is also the default memory column for Task Manager in Windows Vista/7/8.
process explorer working set ws private
We decided to approach this task by gathering memory readings over a period of time. 10 readings were taken for each product at 30 second intervals, totaling 5 minutes of monitoring during idle and another 5 minutes while running a scan. The average score was then taken for each antivirus with all processes created by the application added together. All antivirus software was fully updated before testing using windows 7 32-bit, and the memory readings were taken using Sysinternals Process Explorer.
Below are the results for each antivirus package along with the average Working Set and Private Working Set scores in Kilobytes (KB) while idle and during a scan. The software is in reverse order with the heaviest Private Working Set usage for idle and scan combined listed first, going down to the lowest score and most efficient. If you want to jump straight to the list of results to see how your antivirus got on, they are at the bottom of page 2.
25. ZoneAlarm Free AntiVirus + Firewall
ZoneAlarm memory usage
Number of Processes: 4
Processes Monitored: ISWSVC.exe, vsmon.exe, zatray.exe, ForceField.exe

Idle Working Set (KB): 223,260
Idle Private Working Set (KB): 191,472

Scan Working Set (KB): 287,443
Scan Private Working Set (KB): 226,222

24. Sophos Endpoint Security and Control 10.2
sophos memory usage
Number of Processes: 7
Processes Monitored: swi_service.exe, SavService.exe, SAVAdminService.exe, ALsvc.exe, ALMon.exe, SavProgress.exe, SavMain.exe

Idle Working Set (KB): 216,482
Idle Private Working Set (KB): 192,436

Scan Working Set (KB): 467,817
Scan Private Working Set (KB): 198,452

23. Emsisoft Anti-Malware
Emsisoft Anti-Malware memory usage
Number of Processes: 3
Processes Monitored: a2guard.exe, a2service.exe, a2start.exe

Idle Working Set (KB): 131,158
Idle Private Working Set (KB): 125,337

Scan Working Set (KB): 251,945
Scan Private Working Set (KB): 240,770

22. Quick Heal AntiVirus Pro 2013
quick heal memory
Number of Processes: 8

Idle Working Set (KB): 99,090
Idle Private Working Set (KB): 66,134

Scan Working Set (KB): 273,984
Scan Private Working Set (KB): 227,424

21. McAfee AntiVirus Plus 2013
mcafee antivirus memory usage
Number of Processes: 9
Processes Monitored: McAPExe.exe, mcinfo.exe, mcods.exe, McSACore.exe, mcshield.exe, McSvHost.exe, mcsvrcnt.exe, McUICnt.exe, mfefire.exe

Idle Working Set (KB): 142,375
Idle Private Working Set (KB): 103,518

Scan Working Set (KB): 239,500
Scan Private Working Set (KB): 184,214

20. Ad-Aware Free Antivirus +
ad-aware antivirus memory usage
Number of Processes: 4
Processes Monitored: SBAMSvc.exe, adawarebp.exe, AdAware.exe, AdAwareService.exe

Idle Working Set (KB): 162,540
Idle Private Working Set (KB): 118,728

Scan Working Set (KB): 189,223
Scan Private Working Set (KB): 144,394

19. Bitdefender Antivirus Free Edition
bitdefender free memory usage
Number of Processes: 2
Processes Monitored: gziface.exe, gzserv.exe

Idle Working Set (KB): 115,559
Idle Private Working Set (KB): 91,742

Scan Working Set (KB): 135,836
Scan Private Working Set (KB): 115,795

18. Trend Micro Titanium Antivirus + 6.0.1215
trend micro titanium memory usage
Number of Processes: 6
Processes Monitored: uiWatchDog.exe, uiSeAgnt.exe, coreServiceShell.exe, coreFrameworkHost.exe, AMSP_LogServer.exe, WSCStatusController.exe

Idle Working Set (KB): 102,208
Idle Private Working Set (KB): 72,754

Scan Working Set (KB): 161,926
Scan Private Working Set (KB): 130,022

17. Avira Free Antivirus
Avira Free memory usage
Number of Processes: 6
Processes Monitored: avgnt.exe, avguard.exe, avshadow.exe, avwebgrd.exe, sched.exe, avscan.exe

Idle Working Set (KB): 63,754
Idle Private Working Set (KB): 41,138

Scan Working Set (KB): 199,264
Scan Private Working Set (KB): 157,750

16. VIPRE Antivirus 2013
vipre antivirus memory usage
Number of Processes: 3
Processes Monitored: SBAMSvc.exe, SBAMTray.exe, SBPIMSvc.exe

Idle Working Set (KB): 114,098
Idle Private Working Set (KB): 91,981

Scan Working Set (KB): 134,488
Scan Private Working Set (KB): 104,936

15. NANO Antivirus Free
nano antivirus memory usage
Number of Processes: 2
Processes Monitored: nanosvc.exe, nanoav.exe

Idle Working Set (KB): 176,141
Idle Private Working Set (KB): 53,846

Scan Working Set (KB): 287,284
Scan Private Working Set (KB): 131,201

14. ESET NOD32 Antivirus 6.0.316.0
ESET NOD32 memory usage
Number of Processes: 2
Processes Monitored: egui.exe, ekrn.exe

Idle Working Set (KB): 93,616
Idle Private Working Set (KB): 76,441

Scan Working Set (KB): 103,244
Scan Private Working Set (KB): 82,913

13. Dr.Web Anti-virus
dr.web memory usage
Number of Processes: 6
Processes Monitored: dwarkdaemon.exe, dwengine.exe, dwnetfilter.exe, dwscanner.exe, dwservice.exe, spideragent.exe

Idle Working Set (KB): 92,006
Idle Private Working Set (KB): 66,822

Scan Working Set (KB): 117,973
Scan Private Working Set (KB): 90,430

12. Kaspersky Anti-Virus
kaspersky memory usage
Number of Processes: 2
Processes Monitored: avp.exe, avp.exe

Idle Working Set (KB): 65,625
Idle Private Working Set (KB): 52,218

Scan Working Set (KB): 103,377
Scan Private Working Set (KB): 92,105

11. Bitdefender Antivirus Plus 2013
Bitdefender antivirus memory usage
Number of Processes: 5
Processes Monitored: bdagent.exe, downloader.exe, updatesrv.exe, vsserv.exe, odscanui.exe

Idle Working Set (KB): 81,360
Idle Private Working Set (KB): 47,658

Scan Working Set (KB): 150,478
Scan Private Working Set (KB): 62,877

10. Microsoft Security Essentials
microsoft security essentials memory usage
Number of Processes: 3
Processes Monitored: MsMpEng.exe, msseces.exe, NisSrv.exe

Idle Working Set (KB): 70,484
Idle Private Working Set (KB): 51,750

Scan Working Set (KB): 79,103
Scan Private Working Set (KB): 57,787

9. F-Secure Anti-Virus 12.77 build 100
F-secure antivirus memory usage
Number of Processes: 7
Processes Monitored: fsgk32.exe, fshoster32.exe, FSM32.exe, FSMA32.exe, fsorsp.exe, fssm32.exe, fsblsrv.exe

Idle Working Set (KB): 62,042
Idle Private Working Set (KB): 40,246

Scan Working Set (KB): 92,386
Scan Private Working Set (KB): 66,819

8. AVG AntiVirus Free 2013.0.3272
avg memory usage
Number of Processes: 7
Processes Monitored: avgcsrvx.exe, avgemcx.exe, avgidsagent.exe, avgnsx.exe, avgrsx.exe, avgui.exe, avgwdsvc.exe

Idle Working Set (KB): 194,888
Idle Private Working Set (KB): 34,398

Scan Working Set (KB): 199,628
Scan Private Working Set (KB): 63,403

7. UnThreat AntiVirus Free 2013
unthreat antivirus memory usage
Number of Processes: 2
Processes Monitored: utsvc.exe, UnThreat.exe

Idle Working Set (KB): 13,615
Idle Private Working Set (KB): 8,953

Scan Working Set (KB): 87,027
Scan Private Working Set (KB): 73,778

6. Immunet Free
Immunet memory usage
Number of Processes: 2
Processes Monitored: agent.exe, iptray.exe

Idle Working Set (KB): 40,413
Idle Private Working Set (KB): 29,304

Scan Working Set (KB): 63,475
Scan Private Working Set (KB): 45,510

5. Norton AntiVirus
Norton Antivirus memory usage
Number of Processes: 4
Processes Monitored: ccsvchst.exe, ccsvchst.exe, ccsvchst.exe, ccsvchst.exe

Idle Working Set (KB): 59,304
Idle Private Working Set (KB): 19,362

Scan Working Set (KB): 111,094
Scan Private Working Set (KB): 52,576

4. Panda Cloud Antivirus Free 2.1.1
cloud antivirus memory usage
Number of Processes: 4
Processes Monitored: PSUNMain.exe, PSUAService.exe, PSUAMain.exe, PSANHost.exe

Idle Working Set (KB): 31,714
Idle Private Working Set (KB): 20,340

Scan Working Set (KB): 76,498
Scan Private Working Set (KB): 41,172

3. Comodo Antivirus Free 6.1.275152.2801
comodo antivirus memory usage
Number of Processes: 4
Processes Monitored: cavwp.exe, cis.exe, CisTray.exe, cmdagent.exe

Idle Working Set (KB): 39,664
Idle Private Working Set (KB): 14,954

Scan Working Set (KB): 105,317
Scan Private Working Set (KB): 34,453

2. Webroot SecureAnywhere AntiVirus 2013
webroot secureanywhere memory usage
Number of Processes: 2
Processes Monitored: WRSA.exe, WRSA.exe

Idle Working Set (KB): 3,823
Idle Private Working Set (KB): 2,726

Scan Working Set (KB): 9,949
Scan Private Working Set (KB): 7,673

1. Avast! Free Antivirus 8.0.1483
Avast memory usage
Number of Processes: 2
Processes Monitored: AvastSvc.exe, AvastUI.exe

Idle Working Set (KB): 9,706
Idle Private Working Set (KB): 4,290

Scan Working Set (KB): Resets every 10 seconds
Scan Private Working Set (KB): Resets every 10 seconds

Results and Summary
The result tables are simply split into two, one for the idle memory usage and one for the usage during a virus scan, both in alphabetical order. The colors are self explanatory with green the lightest antivirus and yellow second best. At the other end, red is the heaviest and orange the next most memory hungry.
Average Memory Scores While Idle
Antivirus average memory usage while idle
Average Memory Scores During a Scan
Average memory usage during scan
  • It was quite a surprise to see a couple of antivirus packages actually using an average of nearly 200MB while sitting idle. ZoneAlarm was also very high in both scores during scanning while the Sophos Working Set score more than doubled. Do note that ZoneAlarm does include a firewall though, and doesn’t have a version without it.
  • On the positive side, Webroot SecureAnywhere proves that cloud antivirus packages can be extremely efficient in memory usage, and it was very good in both idle and scanning scores. You’ll also note that both Working Set and WS Private were very close together so it’s also not consuming shared resources from other programs.
  • Avast is the most popular free antivirus around today, and its memory usage is quite impressive. During scanning Avast kept flushing its memory every 10 seconds which kept usage at a very low level, and it should never grow above a small number of Megabytes. Idle resource usage was also very impressive. For efficient memory usage, Avast is the no.1 free antivirus by far.
  • Some small surprises were Comodo, Bitdefender Free and Avira for different reasons. While Comodo seems to have improved its memory efficiency in recent times, Avira appears to have gone in the opposite direction. What used to be possibly the lightest antivirus package you could get for free, is now quite heavy on memory usage, especially during a scan. Although Bitdefender’s memory did fluctuate a lot, on average it still consumes a lot of memory for a program with virtually no features or options.
Final Note: While these results obviously test the antivirus memory usage, they don’t take into account the features present in each application and its detection rates. Therefore you shouldn’t automatically assume lighter is better because a more memory efficient program might not have the amount of features of an antivirus using a few more Megabytes. If your current package is hungry for memory, this does give you a good idea of what the lightest antivirus packages are that you might like to look at a bit closer.


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