If your system gets infiltrated by a rootkit, you might as well just “waste the system entirely,” said a program manager from Microsoft's security solutions group. The point is that rootkits are deliberately constructed to conceal themselves, making it extremely difficult to (a) detect that your system has been rootkitted (compromised with a rootkit), and then (b) remove said rootkit and revert the system to its uninfected state. An active rootkit has full access to your machine. By taking control of the system hardware before the operating system loads, it has the potential to mediate calls to the network and hard drives, and can intercept keyboard and mouse commands. Your have no secrets from a rootkit.
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