It can come as a bit of a shock to find out that your antivirus program does not remove viruses from your computer. Instead, it puts them into quarantine — which means they are still on your computer! Much as you trust your antivirus program, you may wonder if this is safe. If it is safe, do you have to do anything about these quarantined viruses?
First, understand why your antivirus program puts infected files into quarantine. "Infected files" is your clue: a virus does not exist in isolation. It's like getting a gob of chewing gum in your hair: it's hard to get rid of the chewing gum without cutting off some of the hair. To get rid of the virus, you have to delete the infected file.
Your typical antivirus program is not very smart: it can recognize the virus, but has no idea how important the infected file is. What if it deletes a file that you need regularly? That's why the antivirus takes infected files out of commission and leaves the deletion decision to you.
The other reason for putting files into quarantine is false alarms. Sometimes a perfectly law-abiding file looks like a virus carrier. If it's automatically deleted, important programs could just stop working.
What Is Quarantine?
When the antivirus puts an infected file into quarantine, it deletes the file from its original location. It's no longer there and can no longer infect your computer. Then it makes changes to the file so that it cannot run as a program, and puts it in a hidden folder that other programs cannot see or access. It's in a hidden, high-security jail.
How to Deal with Quarantined Files
You can simply ignore quarantined files. For most people, this is uncomfortable. However, if you're not sure how to proceed, it's a safe option while you find out more.
Most modern viruses make their own files, which contain nothing but the virus waiting for an opportunity to infect your computer. If all your programs are running fine, and your system isn't crashing, you can happily delete those files.
You may find files in quarantine that surprise you: files that have been on your computer a long time, or files that a program needs in order to run. These may be the victims of a false alarm.
If a program won't run because a file is in quarantine, use your discretion before restoring it or adding it to exceptions. Read up about the suspected virus and see if it makes sense. Very often, you can send that file to the support team behind your antivirus and they can check it out. If it is a false alarm, they can teach their antivirus program to recognize it.
A quarantined virus is perfectly harmless while in quarantine. It cannot run, and it's well hidden. Human nature, of course, would prefer it entirely off the premises, so once you're sure it's not a file your computer needs — delete!