Australian PC World - Is this antivirus approach safe?

Is this antivirus approach safe?

I use an antivirus program (McAfee) every time I boot up my computer. I regularly scan my hard disk and any floppy disks that are not my own. Occasionally, when I have found a virus on my floppy disk (the virus scan program is on hard disk) I am confused about whether to scan and clean the infected floppy disk from the hard drive, or use a boot disk containing the virus protection program and scan and clean the virus from my boot disk.
My boot disk drive is a 5¼in, and my other floppy is 3½in. At the moment when I have a virus on my 3½in disk I scan and clean the virus from my 5¼in boot disk. I do this because I am afraid if I scan and clean the infected floppy disk from my hard drive, I will infect the hard drive because I am scanning and cleaning the 3½in floppy disk with the write protect tab closed. As you are aware, the write protect tab has to be closed to clean the virus-infected disk.
Am I wrong about the hard drive being infected? And what happens when my hard drive gets infected -- do I scan and clean the virus from a boot disk containing the virus protection program or not? Please help!
- Simon Goeschl

Viruses can be a real pain. Most people aren't really interested in how they work, they just want to know how to get rid of them!
It is normally OK to run your antivirus software from the hard disk, so long as you have scanned the hard disk first. You may also use the DOS command attrib +r *.* in the directory that holds your antivirus software as an extra precaution. This makes all the files read-only.
However, while your system is clean you should take the opportunity to create a DOS boot disk with your antivirus software added to it. From the C: drive, type format A: /s, copy the software and write-protect the disk. This will help you fix an infected hard disk. McAfee's SCAN program will fit on this disk, as would the excellent F-PROT software by Fridrik Skulason (with some careful pruning). Or you can boot with your locked DOS disk and swap it out for the antivirus program disk (also locked) to run the scan.
Not all antivirus programs can fix all viruses. In McAfee's case use the command scan /virlist to see if it will fix your bug. Often it will ask you to use the fdisk /mbr command to clean a master boot record, so copy the Fdisk program to your boot disk as well.
So long as you aren't accessing the hard disk you won't be infecting it. You have two floppy drives so your method is very safe.
- Ian Yates

Category: Viruses
Issue: Dec 1996
Pages: 152