To keep the virus attack on the computer or mobile device at bay, many of us prefer to install antivirus software. Installing an antivirus software keeps the device safe from hackers and malware attacks with the help of the latest updates that protect the device.

Computer viruses have been around since 1949. The antivirus software is the only way to protect data and prevent the effects of any malware and spyware attacks at any point in time. However, there have been times wherein the installed antivirus has not been able to protect the PCs and the data of a company.

This has turned out to be very expensive for companies who installed the software for their requirements.

To some extent, even a protected computer could turn notorious and turn the tables by doing serious damage to the data, mostly because the antivirus failed to protect it. This malware that spreads through the Internet or other programs can cause tremendous harm to the computer. Listed below are the worst PC viruses of all time which created irreparable damage to a large extent

Melissa
Founded in the 1990s, Melissa destroyed Microsoft Windows and Office in a way that no other virus ever had.

Melissa was one of the first major emails activated viruses and also one of the worst in terms of its effect, as it attached itself to Microsoft Office files, something which 99.99% of the users of Windows PCs did at that point of time. Hackers attacked the Windows monoculture by designing a program, Melissa, which exploited bundles of programs such as Word and Outlook, with it being automatically executed in Word 1997 and 2000. The recipients of Melissa conceded message requests to open attached documents, allowing the virus to replicate itself into ‘n’ number of new emails, which were then sent to all the Outlook contacts from the address book. The results in greater email traffic affected the smaller corporate networks at that time, who couldn’t keep up with it. This compelled the industry to briefly suspend operations to deal with Melissa, but not before it spread the damage.

Conficker
The Conficker is widely known as one of the toughest computer viruses in digital world history. Conficker made use of devious malware attack methods with many versions patterned to dodge detection, making it akin to a real biological virus. Conficker’s working banked on remote files’ execution through printing and file sharing protocols on multiple versions of Windows server. It also struck admin passwords and created vast, intricate botnets to further advance the attack. It constantly evolved and had the ability to incapacitate anti-malware events and Windows even in the safest mode. Ten years since its attack in November 2008, Conficker’s effects were persistent and widespread, with almost one million infected computers around the globe.

WannaCry
One of the newest viruses to infect and spread like wildfire is the WannaCry virus which attacked the digital world in May 2017. WannaCry’s attack was a huge leap in the range and effect of ransomware, which is a typical kind of computer malware which holds files hostage in return for ransom payment for the return of those files. WannaCry encrypts its files and asks for bitcoin ransom, which, if not delivered within three days, multiplies and damages the system. The program also threatens to delete the files after seven days if the ransom isn’t paid. The impact was huge, as it affected the National Health Service in the UK, and more importantly FedEx in the country.

Computers have become more powerful over the years, and the disruptive nature of possible viruses have increased greatly. Meanwhile, the stakes have also increased for the presence of adequate cyber security countermeasures. These antiviruses have the ability to not only spread and multiply but also harm the operating systems, causing deletion and infected files. Hence, one of the best ways to keep the computer protected is to install antiviruses from a reliable source.