Answer:
The three applications attacked by Botnet can be attacks drive-by downloads, e-mail or exploiting some vulnerability in browsers such as Google Chrome or Internet Explorer.
Step-by-step explanation:
Botnet is the name by which any group of infected computers is called and which are controlled by a remote attacker. A hacker or a group of them makes a botnet using malware that infects a large number of computers. Computers that are part of the botnet are known as "bots."
Hackers use two methods to infect computers and make them part of their botnet: one is drive-by downloads and email attacks. In the first, the process needs the attacker to find a web page with a vulnerability. In this way, the hacker loads the malicious code on the page and exploits such vulnerability as Google Chrome or Internet Explorer. The malicious code redirects the user's browser to a site controlled by the hacker, from where the bot code is downloaded and installed on the computer. Another type of attack is the sending of a large amount of spam, where a Word or PDF file with a malicious code or a link to a page where the code is hosted is attached.