Few Windows users know this, and no anti-virus software vendor will tell you.
Every year, there are thousands or even tens of thousands of new viruses and malware released for Windows. An anti-virus program unfortunately can't tell whether a file is infected unless the pattern matches something that's already been programmed into its database.
I hear you ask: "How do the anti-virus software developers manage to keep up with adding new viruses to the database?"
The answer is, they don't (see attached graph). The most virulent viruses get put into the anti-virus databases, the less well-known ones don't get put into the database. A gap of some thousands of viruses. Oh, the better anti-virus programs these days can detect the kind of behavior that an active virus will create, but they are entirely toothless at stopping new viruses or lesser-known viruses from actually infecting your system in the first place.
Not only is it a bad idea to 100% trust your anti-virus software, but the idea has become even worse in the three minutes it took you to read this message.
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