April 15th, 2015
Recently, someone I know got a virus on their computer. They weren't sure they'd gotten a virus but their computer was running differently after they'd tried to open a file. They asked me to have a look at it.
At first I thought that it might not be a virus after all, just some software that had been accidentally installed but was unwanted. I went into Control Panel and seek out the program they didn't want. I was able to locate it and uninstalled it. This did not completely resolve the issue though.
A day later, they were complaining that when they launched firefox, something strange happened. So, I took a look again. Upon running firefox myself, I did see that the home page had been changed. I changed this back to the previous home page. However, upon browsing the web myself for a little while I noticed that ads were showing up in places I'd never seen them before on sites I'd recently visited. That's when I began to suspect that the virus was still on the computer. I also noticed that the computer was running rather slowly.
I went ahead and launched msconfig and went to the Startup tab. I was able to see that there was an entry that was definitely not supposed to be there. (I say definitely because you want to be sure that what you are disabling is not important for the system before you disable it). I disabled it on startup and restarted the computer.
The computer booted and was running faster than it had before the restart. This was a good sign. However, the entry was still in msconfig (as it usually is when you simply disable something). Plus, I wasn't sure if I had completely removed the virus - perhaps it was still there lingering. I believe that the ads were still being shown on the websites as I mentioned before. I then decided that it's probably best to perform a System Restore.
I launched System Restore, selected a date before the virus was installed, and began the process.
Upon boot-up, everything seemed to be running just fine with no unusual ads on the websites and the entry removed from msconfig.
In the end, I reflected that often, the best re-course for a computer infected with a virus is to run a system restore, because in my experiences, viruses are so tricky today that the best thing to do is to have System Restore go back to a restore point. Otherwise, you're relying on trying to track down where the virus is and removing it.
I think System Restore can be even better than an anti-virus scan because with System Restore, you're reverting the system (except for documents you created since the restore point) back to a previous state while the anti-virus follows the search and remove mind-set. Still, having an anti-virus isn't a bad idea to try and stop a virus from being installed in the first place or if you can't use System Restore, or don't know when the virus was installed. An anti-virus can be useful in those situations.