01/09/2015
I just had completed rebooting our computer system.
It appears that it had been infected by a virus calling itself DNS Locker (but of course DNS Locker didn't identify itself as a virus).
I had tried 3 different popular antivirus software to remove DNS Locker but none of them worked. All of them confirmed that our computer was well protected after conducting comprehensive checks.
We then proceeded to remove installed software. It appears that DNS Locker initially misrepresented itself as some other reputable brand (Microsoft or Norton Antivirus etc) stating that our computer needed to be protected. When we allowed installation, DNS Locker instated itself as the only authorised entity to remove the software (even overriding the authority of the owner). This prevented us from being able to remove this software. When we found it, it formed parted of internet explorer.
The only way we could effectively deal with this was to reboot the system and use the back up files. Fortunately, our computer, which was Toshiba, was easy to reboot back to its initial state.
There were some programs on the internet asserting that they could remove DNS Locker for free but we weren't gonna put our faith in them. It would be like being saved from wolves, only to be subject to the tyranny of lions.
There are two lessons here. First, rebooting will effectively deal with viruses. Second, do not permit installations especially if they want the exclusive authority to be able to uninstall it .
You may change the computer settings to always ask you before giving permissions to other person to deal with any aspect of the installed software.