If you find your computer working more slowly than usual, the problem may be a rootkit that has borrowed its way into your system. A rootkit is a program that allows a hacker to gain administrator privileges (root access) to a system and then hide all traces of its presence. Once ensconced in the system, it has complete control over the client machine without being detected, allowing the program to wreak all kinds of havoc. By installing rootkits, for example, the hacker gains complete access to the computer, allowing them to freely steal files. Or they can use the infected machine to launch attacks on other computers. Apart from your computer slowing down, the sudden appearance of popup ads and the redirection to unwanted websites are signs that your computer may have a rootkit.
How to Identify and Remove a Rootkit