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A-squared Free Antivirus Version 4.5 Review and Download

24. January 2010
A-squared free main screen 4.5

   A-squared is a venerable free antivirus that includes antispyware and antivirus protection.  According to user and industry reviews, the antivirus is particularly good at detecting Trojans.  In our own tests, we found this consensus to be true and more than exceeded our expectations.  While the program does not include a resident shield, it still can be used in conjunction with other antivirus software to provide dual protection.  We will now take a more in-depth look at all of the program’s functionality.


    The installation of A-squared was very quick.  There was no added toolbar or advertising software, unlike 90% of other free antivirus software.  There were also few configuration options like adding the scanner to the start menu, taks bar, and a desktop shortcut.  After the installation was complete, A-squared started immediately and did not require a restart.  A-squared then prompted for an automatic virus definition update.  The update was large at 7 megabytes but installed over 35,000 Trojan signatures (this was the first indication that a-squared is clearly geared towards anti-Trojan protection).  The update downloaded at about 100 Kilobytes per second and did not appear to have speed limitations like Free AVG.  After the update was complete, a-squared simply needed a program restart and the protection was ready to go.  The installer also included many different languages including Arabic, English, Japanese, Russian, Dutch and many more.

detailed update information a-squared 4.5


    The A-squared Free 4.5 interface was very organized and clean.  I liked the update process because it tells you what was actually download rather than just saying “database updates” like PC tools antivirus etc.  This detailed information theme is repeated throughout the software as every aspect of the software is very informative.  For example, the main page has information about the amount of signatures loaded, quick links to the support center, submitting a suspicious file, and video tutorials on how to use the software.  Unfortunately, A-squared Free does not have taskbar integration like most other free antivirus.  On the other hand, the software does have Windows Shell integration so that this kind forgoes the need for a taskbar icon.  If a user wants to scan a file, all one has to do is right click the file and select scan.
    I also ran into problems with the programs help system.  I would click on the help button but no dialog box would appear.  Emsisoft, if you are listening, please fix this bug in Vista.


    A-squared is a little light on the features but excels at it’s core malware detection and deletion capability.

    User Permissions. Rather than providing password protection, A-squared integrates with the Windows Login to provide access control.  A user can select if a Vista, Windows 7 user can start the scanner, delete objects, start the application, edit quarantine objects, delete quarantine objects etc.  These features are usually absent in free antivirus.

    Quarantine Re-Scan. I really like this feature and it functions as the name implies.  If new virus updates are released and download, the quarantine items will be automatically rescanned.  This is a great feature because A-squared admits that quarantined items may not be actually malicious and ensures that only infected files are quarantined.  In addition, most detection and deletion antivirus do not include quarantine functionality like this software. 

    Beta Updates.  A-squared Free 4.5 offers beta updates, which will give a user the very latest protection.  However, use caution when installing beta updates as they may delete important files.  

    Whitelist.  The software includes a scanner whitelist or trusted file exemption.  In addition, there is also a file extension filter to enable or disable user-defined extensions.

a-squared free 4.5 whitelist and extension filter

Virus/Spyware Scanning and Detection:

    A-squared Free includes multiple Virus Scan Options. They are the quick scan, smart scan, deep scan, and custom scan. All of the scans utilize definition and trace based scanning.  Definition scanning looks at file and compares it to a virus encyclopedia while trace based scanning looks at known malware locations for suspicious files (this is frequently used in antispyware software).
    The quick scan was very quick and completed in less than 4 minutes while the smart scan needed about 1 hour.  Unfortunately, the quick scan and smart scan do not scrutinize the registry as effectively as the other scans.
    The crown jewel of A-squared free is the deep scan technology.  The deep scan detected a virus that no other antivirus reviewed on this blog found.  TVU networks player actually has a Trojan installed and was not deleted after uninstallation of the program.  A-squared also found traces of the Reveler Keylogger that I used in the Kaspersky review.  Unfortunately, the Deep Scan is dreadfully slow.  In 1 hour, the Deep scan was only at 4% completion on the test system.  I will let one infer how long it will actually take to complete a full deep scan.  However, props to Emsisoft for detecting these previously unknown threats.  This episode alone is enough to convince me that A-squared is a must have freeware.
There is also custom scan functionality.  The user can define the locations of the virus scan and whether the scan includes heuristic protection.

a-squared free detected malware for viruses and spyware 4.5

Resource Usage:

    During scanning of traces and the registry, CPU usage was extremely low and  would not go higher than 16%.  Unfortunately, when the scanner moved on to hard drive files, the CPU usage went up to around 50 to 60%.  However, there still was not a noticeable effect on concurrent processes.  One problem I did run into was that Firefox would stop working during a scan.  This is probably because the program scans Mozilla for cookie traces.  A simple restart of the Firefox will solve the problem.
    Memory usage for the A-squared service is a reasonable 12 megabytes while the scanner uses about 125 megabytes during a scan.  These numbers are acceptable when compared to competitors.  


    While I wouldn’t want to uninstall A-squared, the uninstallation is the fastest on the market at only 2 seconds. This goes to show how efficient this program is and that it will not give users problems after uninstall ala Norton.


    A-squared has superior virus and Trojan detection.  This software can work in conjunction with any other antivirus software program and will not cause conflicts.  
Emsisoft has released a free command line scanner that is identical to this version.  However, the command line has capabilities that will make it easier to schedule scans and automate scanner operation.