Antivirus programs will scan your file system, intercept internet connections, contains millions of virus footprints and run in elevated position and embed itself deep into your operating system. All this is done so that it’s hard for a virus to hide from the anti virus software, but it is also a typical trojan behavior.
It’s like somebody having two competing immune systems, you are sure to get autoimmune disease as an immune system behave like a really really bad infection if you don’t understand the mechanic.
By the way, it’s also why antivirus are an ideal vector for infection as they have such high privileges. It is technically dangerous to install an antivirus, you need to trust it. Installing two means you need to trust two, you make yourself more fragile.
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