Despite the many advantages and revolutionary usability of the Windows operating system, it has one significant drawback. To be more precise, we are talking about the susceptibility of the system to attacks of viruses of various types and origin. Let's talk about what boot viruses are, how they work, what harm your computer can do, and how to deal with them.
You began to notice that the computer began to freeze almost immediately after passing the BIOS tests? Reinstalled the system several times or
formatted the hard drive, but did not notice any positive changes? Be careful, because this is the first alarm signal indicating that the so-called boot viruses have settled on the computer.
Their main feature is the affected area. Viruses of this type infect the boot sector of the disk. Moreover, they penetrate into the RAM even before the antivirus program. That is why it is usually quite difficult to find them.
Boot viruses do not always carry destructive functions. However, even in this case, they remain extremely dangerous. Why? Everything is very simple. Errors in programming cause an unstable operation of the operating system, you can lose a lot of important data in the computer's memory. And the installation of a “non-native” system in general can give an unpredictable effect.
You can verify the presence of a boot virus by tracking the interception of interrupt vectors before directly loading the operating system. In the process of transferring control to the master boot record (MBR) sector, all interrupts are processed exclusively with the participation of the BIOS. This significantly reduces the address range. One way or another, the boot virus will intercept some interruptions, due to which it will be able to function. Typically, a combination includes 13h (disk), 8h or 1Ch (timer), 9h (keyboard), 12h (memory size), 21h (MS DOS), 17h (printer). By changing the bootloader a bit, you can see these intercepts, that is, detect the presence of viruses.
If you do not find out in time that boot viruses have got into the computer, you can encounter big problems, the least of which is the need to reinstall the system after cleaning and format the hard drive. In particularly difficult cases, the possibility of reinstalling the system may not be available.
Prevention and treatment of computer viruses is carried out using special utilities. For example, Norton Disk Doctor ("Norton Disk Doctor") has proven itself to be excellent against boot viruses. What else can be done?
1. Disconnect the hard drive from your PC and connect it to another computer with
antivirus installed (it is desirable that this is a high-quality licensed program). After the scan of the hard drive and the treatment of the viruses found is over, you can reconnect the hard drive to your computer.
2. Add the boot function from the CD to the BIOS, and then boot the computer, using the "emergency" disk already. The disk should contain anti-virus software, as well as fresh databases for it.
3. Find a specialist who is able to manually overwrite the boot sector, taking into account the features of your software. This process is a long and laborious, but 100% effective.