Summary
DelCmos is a typical boot sector virus. It is only able to infect a hard disk when you try to boot the machine with an infected diskette in drive A:. At this time the virus infects the Master Boot Record (MBR) of the hard drive, and after that it will go resident to high DOS memory during every boot-up from the hard disk. Once the virus gets resident to memory, it will infect practicly all non-write- protected diskettes used in the machine.
DelCmos allocates two kilobytes of memory while it is active. This can be seen as a decrease in the total amount of DOS memory - it drops from 640kB to 638kB. DelCmos assumes that the machine has full 640kB of DOS memory. This is not always the case, as some systems reserve a kilobyte or two for internal BIOS needs. In this case, DelCmos will just crash the machine every time it's booted after the infection.
DelCmos also assumes the A: drive of the machine to be a 3.5" HD (1.44MB) drive. If it's a 5.25" drive or a 3.5" DD or ED drive, floppies may be corrupted during infection. They can be fixed with the FIXBOOT program.
DelCmos.A contains a routine to overwrite the CMOS SETUP information. DelCmos.B has this activation routine removed; it does nothing except spreads.
DelCmos.A is known to be in the wild in the USA. DelCmos.B was reported to be in the wild in Spain in January 1996.
Removal
Based on the settings of your F-Secure security product, it will either move the file to the quarantine where it cannot spread or cause harm, or remove it.
A False Positive is when a file is incorrectly detected as harmful, usually because its code or behavior resembles known harmful programs. A False Positive will usually be fixed in a subsequent database update without any action needed on your part. If you wish, you may also:
Check for the latest database updates
First, check if your F-Secure security program is using the latest updates, then try scanning the file again.
Submit a sample
After checking, if you still believe the file is incorrectly detected, you can submit a sample of it for re-analysis.
Note: If the file was moved to quarantine, you need to collect the file from quarantine before you can submit it.
Exclude a file from further scanning
If you are certain that the file is safe and want to continue using it, you can exclude it from further scanning by the F-Secure security product.
Note: You need administrative rights to change the settings.
Technical Details
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