Most computer users are aware of the common symptoms of infection:
Missing or new files
If you are experiencing any of these symptoms it would be advisable to register and post at one of the sites offering free malware removal. These forums offer free analysis by trained volunteers. The following is a list of a few reputable sites that provide free malware removal analysis:
If there are no signs of infection, but every so often a file with a strange looking name shows up, we may not be sure whether the file was always present or whether it is something new. It could be a file that is needed by other software on the computer. It could be a remnant of a program that was removed, or it could be malware that is hiding waiting for a component to come along to activate it.
Another possibility would be that the computer has been running smoothly, but the resident anti-virus, flags a file as being infected. How is that confirmed? Occasionally, especially after an update, an anti-virus, anti-malware, or anti-adware application will show a false positive. We certainly do not want to remove a legitimate file, if our computer's security has made a mistake. A second opinion would be a good idea.
One way to help decide what to do is to upload the file to one of the online services that will analyze the file. The basic procedure is usually to copy and paste the path to the file or simply browse and enter in a box the file name to be checked. Follow the prompts. The file will automatically be uploaded from the computer to a dedicated server where it will be scanned. The submission will then be tested against many different anti-virus vendors’ scanners. There will be a report that will show which vendors' products recognize it. In addition, unless told otherwise, these services will provide the sample to their participating vendors. The initial scan is not 100% accurate on all brand new infections, but it is helpful on malware that the the anti-virus vendors already have in their databases.
* Please note that some of the online checkers have file size limits.
Several anti-virus vendors have their own scanners; however these popular online file scanners contribute to many vendors: