Antivirus software is widely believed to have a negative impact on performance, but it's probably a lot less negative than we think, as AV-Test showed during tests found that when using ClamXav, MacKeeper, Kaspersky or Norton, none measurable There was a decrease in performance. There was a measurable difference between Sophos and Trend Micro (2% additional system load) and between ESET and Bitdefender, which contributed around 4% of the total system load.