The effectiveness of malware detection, how well it catches infections, is the chief characteristic to consider when choosing an antivirus program. But resource consumption, how much system resources it uses, is also important. This is especially true on older machines where heavy duty usage by your AV software can bog down the system and make it crawl when running scans.

In a previous article, A Guide to Free Antivirus Software, I reviewed four different free antivirus programs from Avast, Comodo, AVG, and Microsoft. I looked at the security features of each. Now, I am reviewing the resource consumption of the same four programs.

Here I discuss the system requirements, download sizes, and the installation process. I also share the average physical memory (RAM) and processor (CPU) usage I saw while testing. Lastly, I discuss any performance settings that can help control the resource consumption.

avast! Free Antivirus 6 - avast! Free Antivirus 6 supports Windows 2000 Pro SP4, XP SP2 or SP3, Windows Vista, and 7. It requires at least a Pentium III processor with 128MB of RAM and 200MB of free hard disk space.

The install file is fairly large at 56.2MB, but no additional downloads are required. The installation took only about three minutes, included an initial quick scan, and didn’t even require a reboot. After the install, it quickly updated the virus definitions.

Here are the memory usage numbers I saw for the two running avast processes:

  • Avastui.exe (avast! Antivirus) 6,044K
  • AvastSvc.exe (avast! Service) 14,442K and 37,042K during scanning

While idle, the total memory usage was around 20,486K. During the quick scan I ran, the total increased to about 43,086K, and CPU usage was about 5 percent to 15 percent. It took 11 minutes and scanned 25,625 items.

In the settings I found a couple resource control features. In the scanning settings, you can choose a scan priority: High (default), Normal, or Low. The higher the priority, the more system resources it will use. I also found avast uses a caching feature to help speed up real-time and manual scans. It does this by not rescanning files previously marked as safe until a reboot or a virus definition update.


avast fig 1

I also found two useful scan scheduling settings for laptops: you can enable it to not start if running on batteries and pause if you begin to use batteries.


avast fig 2

COMODO Internet Security 5.5 - COMODO Internet Security (CIS) supports Windows XP SP2 or higher, Vista, and 7. It requires 128 MB of RAM and 350MB of free disk space.

The download file at 59.7MB was the biggest of those I reviewed, but I didn’t have to do any further downloading during the install. Like avast, the installation only took about three minutes and didn’t require a reboot. But it did require a 10 minute update process, including a 142MB download.

Here is memory usage numbers I saw for the four running processes:

  • Cfp.exe (COMODO Internet Security) 8,904K
  • Cmdagent.exe (COMODO Internet Security) 10,592K and 52,616K during scanning
  • Clps.exe (COMODO GeekBuddy) 27,520K
  • Clpsls.exe (COMODO livePCsupport Service) 2,876K

While idle these add up to 49,892K of memory usage. They recommend a full scan after install, but they also offer a critical areas scan, which is what I ran. During the six minutes it took to scan 201,909 items, the memory usage was very sporadic but averaged around 91,916K and 5 percent to70 percent CPU usage.

Keep in mind, the bottom two processes in the list above are for the optional GeekBuddy service COMODO provides. This is included in the install by default but you can easily opt out of it during the installation. If you do, you’ll see a reduction in resource consumption. For instance, I saw memory usage around 19,496K at idle and 61,520K while scanning.

Unlike with the other programs, I didn’t find any settings in CIS to limit CPU or resource usage.