These can sometimes be used for good by adding new functionality to another application, such as color highlighting of keywords in MSN Messenger chat boxes, for example.
Most of the time hooks are used by malicious applications like a Keylogger, Trojan, Virus, Spy Software or Worm to hook into a third party application so that they can pretend to be that application.
By doing this they are able to make the third party application do things that they normally would not do.
Most anti-virus or firewall software would allow the activities to happen because they are being executed by a trusted program, even though it is a function from a DLL that was hooked into the application that is doing these malicious activities.
If SpyCop Cloak is warning you that an application is attempting to install a hook, we highly recommend that you deny this from happening unless you absolutely trust the application in question.
