Viruses grow and grow, also computer viruses. More than 550,000 malicious viruses are detected every day.
Do we know what a computer virus is? It could be summed up by saying that it is any attempt to access a computer without the permission of its owner through a malware program. The purpose is to steal or destroy computer data.
There are many types of viruses. We could classify them according to their origin, ability to spread, location, and destructive nature. Let’s dig deeper.
boot sector virus
It is the one that infects the master boot record (MBR) of the storage device. It injects its code into the hard drive’s partition table and then enters the main memory after the computer restarts.
Problems that arise after infection include boot problems, instability in system performance, and the inability to locate hard drives.
Since this virus infects the boot sector, it can be difficult to remove, and in most cases, users don’t even know that they have been infected until they scan their computer with an antivirus program.
The good news is that with the decline of floppy disks, these viruses are rarely common now because modern operating systems have built-in boot sector protection, making it challenging to find the MBR.
How to protect ourselves? Use a write-protected disk and do not restart the computer with unknown external disks connected.
It quickly enters the main memory, infects all programs/files/folders defined in the Autoexec.bat path, and then deletes itself. It can also destroy the data present on a hard drive or USB connection to the computer.
They usually spread when the file containing them is executed. If you don’t run or open the file, it shouldn’t spread to other parts of your device or your network.
Protection: Direct action virus is easily detected with antivirus, and all infected files can be fully restored.
They are the ones that remove the data and replace the original code with their own. They do not change the content or the size of the file.
In addition, this type of virus can not only make applications not work but also encrypt and steal your data during execution.
Protection: The only way to get rid of this virus is to delete all infected files, so it’s best to keep your antivirus program up to date, especially if you’re using Windows.
web scripting virus
Any web page can inject hidden code in the header, footer or root access file. It usually spreads with infected advertisements that appear on web pages.
They can be, in turn, persistent viruses (they can impersonate a user) or non-persistent (it attacks the user without realizing it and remains hidden forever).
One way to fight these viruses is to disable scripts, use cookie security, or install real-time web browser protection software.
They were also known as Cluster virus, which infects the file by changing the DOS directory information. DOS is altered to point to the virus code instead of the original program.
Protection: Install antivirus to relocate missing files
Polymorphic viruses encode themselves using different encryption keys each time they infect a program or create a copy of themselves. Due to the other encryption keys, it is difficult for antivirus software to find them.
Mark Washburn created the first known polymorphic virus (named “1260”) in 1990. It infects .com files in the current or PATH directories upon execution.
memory resident virus
It can affect files running on the PC, as well as files that are being copied or renamed.
The virus lives in the primary RAM and is activated when the computer is turned on.
There are two types of memory resident viruses:
Fast infectors: These are specifically designed to corrupt as many files as possible as fast as possible. They are straightforward to notice due to their adverse effects.
The slow infectors. Gradually degrade the performance of the computer. They spread more widely because they can go unnoticed for much longer.
If you’re lucky, your antivirus software may have an extension or plug-in that can be downloaded to a USB flash drive and run to remove the virus from memory. If not, you may need to reformat the machine and restore everything you can from the available backup.
You can also talk about other kinds of viruses, such as:
Fat virus (FAT virus)
In addition, we must talk about other malicious programs that are not viruses but are equally dangerous, such as Trojan horses, worms, and logic bombs.