Question

how many type we inject virus in other computer amd websites

Answer 1

there are so many computer virus such as computer virus called
1. worms
2.ransomware
3.spyware
4.adware
5.trojan horses
6.keyloggers
7.rootkits
8. bootkits
9.malicious Browser Helper Object (BHO) and other malicious software these are the virus can harm computer and genuine websites

hope it's helpful

Answer 2

Unpatched software

The last topic we’ll discuss is one that most people overlook. Another way you can put your computer at risk of a virus infection is through unpatched software. Security holes unknown to software maker or antivirus vendors are also known as Zero-Day vulnerabilities. Exploits that stem from security holes affect software companies small and large, including the likes of Microsoft, Apple and Google.

During March 2013, Oracle released emergency patches to Java, a popular plugin used to view content on browsers and applications because of a vulnerability that allowed hackers to exploit computers without minimal barriers of entry.3. Online Ads

Malicious online ads, also known as Malvertising, is just another way your computer can get a virus without any realization or traceable evidence. Criminals often place clean ads on trusted websites and leave them in place for a while to gain credibility. After some time passes they put a malicious code in the ad that infects your computer when clicked on.2. Downloading software from malicious sitesWhen your computer gets infected with a virus, it’s common for someone to joke and say, “What kind of questionable files were you downloading?” It’s a common misconception that viruses only come from inappropriate or problematic websites, but viruses are a danger everywhere on the internet. Even if you're downloading software from a trusted source, there are still traps that can infect your computer.

For example, a user wants to download the Google Chrome browser and clicks on the link. The link provides the Google Chrome download file, which the user installs successfully. Unbeknownst to the user, the download package was injected with a virus and the computer is now infected (this problem actually occurs very often)