Avast! is an antivirus computer program available to Microsoft Windows, Mac OS X and Linux users, with a user interface available in 41 languages.
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Pro Decent anti-virus protection
Con Tries too hard to sell you the paid version
Con Makes your system slower than usual
Even though scans are not being run in background, it will slow your system.
Con Opt-out installation of Google Chrome
These advertising tactics are simply unacceptable
Con Detection rate isn't too solid
Avast! is not the sort of antivirus product to give you peace of mind. In practice, it does miss some malware every now and then. You'll need backup virus protection, which raises the question why you should get Avast in the first place.
Con Too noisy
Avast! has sounds turned on by default. It also has a lot of blinky features of questionable use.
Con Expires after a year leaving computer exposed to new viruses
Expires and stops updating after a year after which the user's computer may become infected by new viruses not covered by existing patterns.
Con "Smart Screen" feature
When running an unknown application, avast will run it wrapped in a sandbox environment first for scanning, then kill the process and re-run it again. A lot of applications do not like this.